Applied High-Tc Superconducting Electrical Machines

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科技词汇

（科技<汉译英>）播客video blog on the Internet首航maiden voyage网恋online love affair遥感remote sensing导航栏navigation bar智能卡smart card信息港info port月球车lunar rover背投屏幕rear projection screen边缘科学boundary science电信业务the telecommunication sector感知技术perceptive technology观测装置stereo camera光纤通信optical fiber communication火炬计划Torch Program机器语言machine language基因工程genetic/gene engineering技术产权technology property rights技术更新technological upgrading尖端技术state –of-the-art technology科技含量scientific and technological content 可视图文visual pictures and literature克隆技术cloning technology空间探测space exploration蓝牙技术Bluetooth technology立体农业stereo farming模拟技术analog technology偏离轨道veer off course气象卫星meteorological satellite前瞻技术foresight technology清晰影像 a full high-resolution picture燃料电池fuel cell人机交互human-computer interaction认证授权certificate authority实时处理real-time processing试管婴儿test-tube baby手动搜索manual search数字机遇digital opportunities双星计划Double Star Program通信卫星communication satellite同步卫星geostationary satellite网格计算grid computing网络课堂online class网络数据network database网络诈骗cyber fraud网上冲浪surf the Internet网上购物online shopping网上聊天online chatting网上通信online navigation卫星导航satellite navigation无人飞船unmanned spaceship无土栽培soilless cultivation无性繁殖asexual reproduction新能源观new thinking on energy development信息高地information highland移动计算mobile computing载人航天Manned Space Flight自主计算autonomic computing字符识别character recognition网络综合症net synthesis国际空间站International Space Station技工贸结合integrate scientific and technological developmentwith industrial and trade development蛋白质工程protein engineering模拟计算机analog computer数字化战场digitize the battlefield数字显示器digital display硬盘驱动器hard-disk drive无线寻呼网radio paging network转基因动物genetically modified animal (GMA)转基因食品genetically modified food (GMF)智能终端机intelligent terminal产品科技含量technological element of a product大容量高速率high-capacity and high-speed电子商务认证E-business certification多任务小卫星small multi-mission satellite (SMMS)国防关键技术defense critical technology基础传输网络basic transmission network技术合作活动technological cooperation process高温超导电缆high-TC superconducting cable空间物理探测space physics exploration交互信息网络interactive information network科教兴国战略the strategy of revitalizing China through science and education太阳能电池板solar panel数字图像处理digital image processing密钥加密技术Key Encryption Technology网上交易平台online trading platform消除数字鸿沟bridge the digital divide信息基础设施information infrastructure虚拟现实技术virtual reality technology月球探测卫星lunar probe推广科技成果turn laboratory achievements intocommercial/mass production无线电导航设备radio navigation device先进的安全技术leading-edge security technologies新兴高科技产业new high-tech industries国家重点实验室national key laboratory加快信息化进程accelerate the informationization process宽带高速信息网high-speed broadband information networks重组DNA技术recombinant DNA technology全球电子商业框架 a framework for global E-commerce信息的选择性传播selective dissemination of information信息社会协调发展coordinated development of information society信息通讯管制体系infocom regulation system改善社会信息服务render better information services to society空间环境探测系统space environment detector system知识创新工程试点pilot knowledge innovation project科学技术教育与培训S&T education and training前沿性、交叉性研究pioneering and interdisciplinary research以信息化带动工业化industrialization through informationization月球的重力场和环境gravity field and environment of the moon有机（生化）纳米材料organic nanomaterial中国已成功地发射了第一颗实验通讯卫星。

毕业设计课题(论文)任务书

毕业设计课题（论文）任务书系部：计量工程系专业：供用电技术专业班级供电08—1指导老师（含职称）：刘海客课题（论文）题目：配电系统中分布式电源的接入一：设计（论文）的主要任务及目的供用电技术专业毕业设计是实现本专业人才培养目标要求的重要阶段。

通过本课题的毕业设计，学生将加深、巩固对供电、用电相关基础知识的理解，并学会利用所学专业基础知识解决供电、用电相关岗位的工作上遇到的实际问题。

本课题要求基于配电系统中分布式电源的接入分析设计，其目的和任务是：（1）巩固《电力系统分析》的相关基础知识，锻炼学生进行电力系统分析的能力；（2）巩固《供用电设备》所学知识，锻炼学生进行组合各种供用电设备的实践能力；（3）巩固《供用电网络继电保护》，锻炼学生根据元件参数设计继电保护的能力；（4）巩固所学的电气主接线知识和绘图知识，锻炼学生应用电气CAD等软件绘制工厂变电所计算用电气主接线简图的能力；通过本次毕业设计，要求学生进一步加深对基础理论的理解，扩大专业知识面，完成教学计划规定的基本理论、基本方法和基本技能的综合训练，力求在收集资料、查阅文献、调查研究、方案制定、计算机处理、撰写论证、口述表达等方面加强训练，实现所学知识向能力的转化。

同时培养学生严肃认真的科学态度，求实的工作作风和良好的协作精神、创新意识。

毕业设计应充分体现“教师指导下得以学生为中心”的教学模式，以学生为认知主题，充分调动学生的积极性和能动性，重视学生自学能力和自组织能力的培养。

要求学生按时完成论文写作任务，灵活运用资料，切记不可抄袭。

二：设计（论文）的基本内容：1．设计资料1. PU TTGEN H B , MACGREGOR P R , LAMBERT F C. Distributed generation : semantic hype or the dawn of a new era IEEE Power and Energy Magazine , 2003 , 1 (1) : 22-29.2. 王成山，王守相．分布式发电供能系统若干问题研究．电力系统自动化，2008，32（20）：1-4,31．Wang Chengshan, Wang Shouxiang．Study on Some Key Problems Related toDistributed Generation Systems．Automation of Electric Power Systems, 2008,32(20):1-4,31．3. 李天友，金文龙，徐丙垠．“配电技术”．中国电力出版社，北京，2008年3月．Li Tianyou, Jin Wenlong, Xu Bingyin．“Distribution Technology”，ChinaElectric Power Press, Beijing, March,2008．4. 梁有伟, 胡志坚, 陈允平. 分布式发电及其在电力系统中的应用综述. 电网技术, 2003, 27 (12):71-75,88.Liang Youwei, Hu Zhijian, Chen Yunping. A Survey of Distributed Generation and Its Application in Power System. Power System Technology, 2003, 27(12):71-75,88.5. 严俊，赵立飞. 储能技术在分布式发电中的应用. 华北电力技术，2006，第10期，16-19.Yan Jun, Zhao Lifei. Energy Storage for Distributed Generation. North China Electric Power, 2006, No.10, 16-19.Deng Zigang, Wang Jiasu, Wang Suyu etc..Status of High Tc superconducting Flywheel Energy Storage System. Transactions of China Electrotechnical Society, 2008, 23(12):1-10.6. 胡学浩．分布式发电（电源）技术及其并网问题．电工技术杂志，2004，第10期, 1-5. Hu Xuehao. Distributed Generation and Grid-connected Technology. Electric Engineering,2004, No.10, 1-5.7. 鲁宗相‘王彩霞‘阂勇‘周双喜‘, 吕金祥, 王云波，微电网研究综述，电力系统自动化，2007，31（19）：100-107.Lu zhongxiang. Wang Caixia. Min Yong. Zhou Shuangxi. Lu Jinxiang, Wang Yunbo, Overview on Micro Grid Research, Automation of Electric Power Systems, 2007,31(19):100-1078. Christian Schulz. Gerold R?der. Michel Kerrat, Virtual Power Plant With Combined Heat and Power Micro-units, CIRED Seminar 2008: SamrtGrids for Distribution,June,2008,Frankfut参考网站国农村电气化信息网、输配电设备网、北极星电力网、国家电力信息网、中国电力新闻网2．设计内容（1）分布式电源概述1.1分布式电源的概念1.2 分布式电源系统结构1.3 分布式电源的技术特点（2）分布式电源的发展现状2.1国外分布式电源发展2.2 国内分布式电源发展（3）分布式电源接入对电网的影响3.1对电网规划的影响3.2对线路上潮流的影响3.3对网损的影响3.4对电能质量的影响3.5对系统保护的影响3.6对可靠性的影响3.7非正常孤岛问题3.8其他方面的问题（4）分布式电源接入电网的环境和条件（5）分布式电源的相关国家标准5.1分布式电源接入配电网的技术规定5.2分布式电源接入配电网的测试规定5.3分布式电源接入配电网的运行控制规范5.4分布式电源接入配电网的监控系统功能规范（6）分布式电源并网关键技术6.1国外经验6.2分布式智能发电技术6.3分布式电源信息交互技术6.4分布式电源规划设计技术6.5适用于分布式电源新型储能技术6.6分布式电源并网运行调度技术6.7分布式电源标准体系和检测技术（7）分布式电源技术展望（8）总结3．基本要求1、论文应做到中心突出，层次清楚，结构合理；必须观点正确，论据充分，条理清楚，文字通顺；并能进行深入分析，见解独到。

美联英语：高科技类新词汇汇总

美联英语提供：美联英语：高科技类新词汇汇总小编给你一个美联英语官方试听课申请链接：/?tid=16-73374-0 3C 融合（3c fusion）3G（3rd Generation）3R技术（3R techniques）4A（Anyone Anytime Anywhere Anything）CG（Computer Graphics ）DVD（Digital Versatile Disk，多功能数码光盘）EVD （Enhanced Versatile Disk，增强型多媒体盘片系统）Open AccessSOI材料（Silicon on Insulator Materials）Wi－Fi技术（Wireless Fidelity）阿尔法客车”（AlphaBus）爱普（APIEL：Advanced Placement International English Language）按需计算（On－Demand Computing）白色农业（white agriculture）办公自动化（OA：Office Automation）半导体材料（semiconductor material）比较医学（Comparative Medicine）并行工程（Concurrent Engineering）博客（Blog/Blogger）超级网站（Super Website）城市垃圾管理的三C原则（Clean Cycle Control）创新决策权（Authority innovation－decisions）磁悬浮列车（Magnetically Levitated Train）大规模杀伤性武器（Weapons of mass destruction）（陶子）中微子（Tau neutrino ）大科学（Big Science）地球模拟器（Earth Simulator）地球资料卫星（earth resources satellite）地震矩规模（moment magnitude scale）电子现金（Electronic Cash）电子支票（Electronic Check）动漫（Comic and Animation）都市农业（Urban Agriculture或Agriculture in City Countryside）二恶英”（Dioxin）非典型肺炎（Atypical Pneumonias）分布式计算（Distributed Computing）分布式能源（distributed energy sources）分子遗传学（Molecular genetics）疯牛病（Mad Cow Disease）干扰素（Interferon）干细胞（Stem Cells）干燥综合征（Sjogren Syndrome，SS）高技术（High T echnology，简称Hi－tech）高技术战争（high－tech warfare）高温超导电缆（High－TC Superconducting Cable）高温超导体（High－TC Superconductor）公共密钥基础结构（Public Key Infrastructure，PKI）供应链管理（Supply Chain Management）光纤通信（Optical Fiber Communication）国防高技术（defense high technology）国防关键技术（defense critical technology）国防信息基础结构（DII Defence Information Infrastructure）国际空间站（ISS（International Space Station）互联网时间（Internet Time）机顶盒（Set－Top Box，简称STB）基础研究（Basic Research）基因歧视（Gene Discrimination）基因枪法（particle bombardment）基因疫苗（Gene Vaccine）基因诊断（Gene Diagnosis）基因指纹法（Genetic Fingerprint）基因治疗（Gene Therapy）极端制造（Extreme manufacturing）集束炸弹（Cluster bombs）技术推广与科技服务季节失调症（maladjustment in season）建筑设备自动化系统（Building Automation System，简称BAS）健康住宅（Healthy Building or Healthy House）降水概率（precipitation probability）降水量（rainfall precipitation）金属玻璃（Metallic Glasses）京都议定书（Kyoto Protocol）精确农业（Precision Agriculture）精神领袖（Spiritual leader ）精准农业（Precision Agriculture）巨磁电阻材料（Giant Magnetoresistance Materials）聚合酶链反应（Polymerase Chain Reaction ，PCR）军事革命（revolution in military affairs）科学技术教育与培训（S&T education and training）科学素养（Scientific Literacy）可视图文（Visual pictures and literature）空间站（space station）空中交通管制（air traffic control―ATC）蓝色农业（blue agriculture）蓝牙技术（Bluetooth）立体农业（stereo farming）量子纠缠（Quantum Entanglement）量子密码术（Quantum cryptography）量子隐形传送（Quantum Teleportation）硫污染（Pollution by Sulfur）绿色GDP（Green GDP）绿色纤维（Lyocell fibre）绿箱政策（GreenBox Policies）密钥加密技术（Key Encryption T echnology）敏捷制造（Agile Manufacturing）（20030731）纳米材料（nano material）与纳米粒子（nano particle）纳米机器人（Nano Robot）纳米科学技术（NanoST （Nano Science and Technology））纳卫星（Nano－Satellite）农业产业化（Agriculture Industrialization）欧洲洁净空气”计划（CAFE （Clean “Air For Europe rogramme”）贫铀弹（Depleted Uranium Bomb）平均无故障工作时间（mean－time－between－failures ―MTBF）普适计算（Pervasive Computing）气象卫星（meteorological satellite）千年生态系统评估（Millennium Ecosystem Assessment）清洁生产（Cleaner Production）全球定位系统（Global Positioning System，简称GPS）全球警报与反应网络（Global Out－break Alert and Response Network）燃料电池（Fuel Cell）人工乘客（Artificial Passenger）人类脑计划（Human Brain Project）人文发展指数（HDI）认证中心（Certificate Authority，简称CA）柔性制造技术（flexible manufacturing technology―FMT）朊毒体（Prion）深空探测（Deep Space Exploration）生命体征（vital signs）生命体征（vital signs）生态预报（ecological forecasting 或ecological）生物安全（Biosafety）生物防治（biological control）生物经济（Bio－economy）生物库”计划（“Biobank”Project ）生物入侵（Biological invasion）生物芯片（Biochip）生物信息学（Bioinformatics）生物质能（Biomass Energy）时间旅行（Time Travel）试验发展（Development）受众分割（Audience segmentation）数字地球（Digital Earth ）数字地球（Digital Earth）数字电视（Digital TV，简称DTV）数字鸿沟（Digital Divide）数字化战场（digitizing the battlefield ―DB）数字视频广播（DVB “Digital Video Broadcast”）数字图书馆（DL “Digital Library”）数字显示器（Digital Display）数字现金（Digital Cash）数字音频磁带（DAT “Digital Audio Tape”）数字自然音影技术（DNA “Digital Natural Audio/Video”）双星计划（Double Star Programme）水资源（Water Resources）酸雨（Acid Rain）外科手术式打击（Surgical strike）网格计算（Grid Computing）网络数据库（Network Database）网络综合症（Net Synthesis）危机管理（Crisis Management）微机电系统（Micro Electro－Mechanical Systems，MEMS）微流体技术（Microfluidics Technology）温室效应（Greenhouse Effect）物理农业（Physical Agriculture严重急性呼吸道综合症（SARS：Severe Acute Respiratory Syndrome）阳光政策（Sunshine policy）遥感（Remote Sensing）遥医学（Telemedicine）液晶（Liquid Crystal）液晶（liquid crystal）液晶显示器（Liquid Crystal Display，LCD）一票否决权（veto power）医学遗传学（medical genetics）医院信息系统（Integrated Hospital Information System，IHIS）移动计算（Mobile Computing）移动上网（WAP）遗传筛查（Genetic Screening）应用研究（Application Research）营养免疫（Nutrition Immunology）有机（生化）纳米材料（Organic （Biochemical）Nanomaterial）预发式计算（Proactive Computing）远程呈现（telepresence）远程医学（Telemedicine）载人航天（Manned Space Flight）载人航天（manned spaceflight）摘菊使者（Daisy Cutter）知识管理（Knowledge Management，简称KM）知识经济（The Knowledge Economy）知识引擎（Kengine）知识与资源管理（KRM：Konwlege & Resource Management）脂质体（Liposome）植物全息现象（Plant Holographic Images）中国强制认证（CCC“China Compulsory Certification”）重组DNA技术（Recombinant DNA Technology）转基因动物（Genetically Modified Animal）转基因食品（Genetically Modified Food）准晶（Quasicrystal）准一维纳米材料（Quasi－one－dimensional Nanometer Material）资源安全（Resource Security）自主计算（Autonomic Computing）综合性安全（Comprehensive Security，或非传统安全）总部经济（Headquarters Economy）组织培养技术（Tissue Culture Technology）太空农业（Space Agriculture）太空行走（Walking in space）太阳风暴（Solar Storm）太阳能（Solar Energy）炭疽（Anthrax）炭疽（anthrax）唐氏综合症（Downs Syndrome）提高战略运算能力计划Accelerated Strategic Computing Initiative，ASCI 体细胞遗传学（somatic genetics）通信卫星（communication satellite）西尼罗河病毒（West Nile virus）消费电子（consume electronics）信息材料（information materials）信息技术外包（IT Outsourcing）信息经纪人（Information Broker）信息战（information warfare―IW）休闲农业（Recreational Agriculture）虚拟口腔（DentAART）虚拟人（Visual Human）虚拟人（Visual human）虚拟天文台（Virtual Observatory）虚拟现实技术（Virtual Reality Technology）循环经济（Recycling Economy / Cyclic Economy）美联英语：。

准一维超导体K2Mo3As3中超导电性的再现

Reemergence of superconductivityin pressurized quasi-one-dimensional superconductor K2Mo3As3Cheng Huang1,2*, Jing Guo1,4*, Kang Zhao1,2*, Fan Cui1,2, Shengshan Qin1,2, Qingge Mu1, Yazhou Zhou1, Shu Cai1,2, Chongli Yang1, Sijin Long1,2, Ke Yang3, Aiguo Li3,Qi Wu1, Zhian Ren1,2, Jiangping Hu1,2 and Liling Sun1,2,4†1Institute of Physics and Beijing National Laboratory for Condensed Matter Physics,Chinese Academy ofSciences, Beijing 100190, China2University of Chinese Academy of Sciences, Beijing 100190, China3Shanghai Synchrotron Radiation Facilities, Shanghai Institute of Applied Physics, Chinese Academy of Sciences,Shanghai 201204, China4Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China Here we report a pressure-induced reemergence of superconductivity in recently discovered superconductor K2Mo3As3, which is the first experimental case observed in quasi-one-dimensional superconductors. We find that, after full suppression of the ambient-pressure superconducting (SC-I) state at 8.7 GPa, an intermediary non-superconducting state sets in and prevails to the pressure up to 18.2 GPa, however, above this pressure a new superconducting (SC-II) state appears unexpectedly. High pressure x-ray diffraction measurements demonstrate that the pressure-induced dramatic change of the lattice parameter c contributes mainly to the emergence of the SC-II state. Combined with the theioretical calculations on band strcture, our results suggest that the reemergemce of superconductivity is associated with the change of the complicated interplay among different orbital electrons, driven by the pressure-induced unisotropic change of the lattice.The discoveries of the copper oxide and iron-based high-T c unconventional superconductors have generated considerable interest over the past 30 years due to their unusal superconducting mechanism and great potential for application. A common feature of these superconductors is that they contain d orbital electrons in their quasi-two-dimentional lattice that results in intriguing superconductivity and other exotic properties [1-6]. Recently, a family of CrAs-based superconductors with superconducting transition temperatures (T c) of 2.2 - 8.6 K were found in X2Cr3As3 (X=Na, K, Rb, Cs) compounds, which possess the features of containing d orbital electrons in a quasi-one-dimensional lattice [7-10] and many unconventional properties [11]. Soon after, a new family of quasi-one-dimmensional MoAs-based superconductors Y2Mo3As3(Y= K, Rb, Cs) with T c s from 10.4 K to 11.5 K was discovered [12-14]. The properties of the upper critical field and specific-heat coefficient of the Y2Mo3As3 superconductors are similar to those of X2Cr3As3.The crystal structure of the Y2Mo3As3 superconductors is same as that of X2Cr3As3, crystallized in a hegxagonal unit cell without an inversion symmetry [12]. The alkali metallic atoms serve as the charge reservoir and the Mo-As chains are responsible for their superconductivity [12]. Since these superconductors host non-centrosymmetric structure that usually connects to the unconventional pairings and exotic physics, they have received considerable attentions in the field of superconductivity researches [15-19].Pressure tuning is a clean way to provide significant information on evolution among superconductivity, electronic state, and crystal structure without changing the chemical composition, and eventually benefits for a deeper understanding of the underlying physics of the puzzling state emerged from ambient-pressure materials[2,20-24]. Earlier high pressure studies on X2Cr3As3(X=K and Rb) below ~4 GPa found that its superconductivity can be dramatically suppressed by external pressure [25,26], however, high pressure studies on the K2Mo3As3 superconductor is still lacking. In this study, we performed the in-situ high pressure transport measurements on the K2Mo3As3 sample up to 50 GPa to know what is new for this compound under high pressure.The polycrystalline (wire-like) samples, as shown in the inset of Fig. 1a, were synthesized using a conventional solid-state reaction method, as described in Ref. [12]. High pressure was generated by a diamond anvil cell made from a Be-Cu alloy with two opposing anvils. Diamond anvils with 300 culets (flat area of the diamond anvil) were used for the experiments. In the resistance measurements, we used platinum foil as electrodes, rhenium plate as gasket and cubic boron nitride as insulating material. The four-probe method was employed to determined pressure dependence of superconducting transition temperature. In the high-pressure ac susceptibility measurements, the sample was surrounded by a secondary coil (pickup coil), above which a field-generating primary coil was wounded [21, 27]. High-pressure angle dispersive x-ray diffraction (XRD) measurements were carried out at beamline 15U at the Shanghai Synchrotron Radiation Facility. A monochromatic x-ray beam with a wavelength of 0.6199 Å was adopted. The pressure was determined by ruby fluorescence method [28]. Given that the sample reacts with the pressure transmitting mediums under pressure, no pressure medium was adopted in all high-pressure measurements.Figure1a shows the temperature dependence of the electrical resistance of the ambient-pressure sample with an onset T c of about 10.4 K, in good agreement with the previous report [12]. Figure 1b-1d show the high pressure results. It is seen that theresistance at 1.2 GPa shows a remarkable drop starting at ~9.2 K and reaches zero at ~ 4.5 K (inset of Fig. 1b), indicating that the applied pressure decreases the onset T c from 10.4 K to 9.2 K. Upon further increasing pressure to 1.5 GPa, the sample loses its zero resistance and its T c shifts to lower temperature, reflecting that the superconductivity of this polycrystalline sample is highly sensitive to the applied pressure. Then, T c decreases continuously with a rate of d T c/d P= -1.19 K/GPa until cannot be detected at 8.7 GPa down to 1.6 K (Fig. 1b). The non-superconducting state persists to the pressure of 18.2 GPa, at which unexpectedly another remarkable resistance drop is found at ~ 4.6 K (Fig. 1c). This drop becomes more pronounced with further compression (Fig. 1d), and plunges about 92% at 47.4 GPa. Moreover, we find that the onset temperature of the new resistance drop shifts to high temperature with increasing pressure initially (the inset of Fig. 1d), reaches a maximum (~8.1 K) at ~ 30 GPa and saturats up to ~38 GPa. By applying higher pressure to 47.4 GPa, the temperature of the drop displays a slow decline (inset of Fig. 1d).To confirm whether the new resistance drop observed in K2Mo3As3 is related to a superconducting transition, we applied magnetic field to the sample subjected to 19.6 GPa and 41.8 GPa, respectively (Fig. 2a and 2b). It can be seen that this new resistance drop shifts to lower temperature with increasing magnetic field and almost suppressed under the magnetic field of 3.5 T and 4.0 T for the compressed sample at 19.6 GPa and 41.8 GPa, respectively. These results indicate that the new resistance drop should be resulted from a superconducting transition. The alternating-current (ac) susceptibility measurements were also performed for the sample subjected to 20 GPa - 44 GPa down to 1.5 K, the lowest temperature of our instrument, but the diamagnetism is not detected. By our analysis, the failure of the measurements on the diamagnetism may be related to the low volume fraction of the pressure-induced superconducting phase.We extract the field (H) dependence of T c for K2Mo3As3 at 19.6 GPa and 41.8 GPa (Fig. 2a and 2b) and plot the H(T c) in Fig. 2c. The experimental data is fitted by using Ginzburg-Landau (GL) formula, which allows us to estimate the values of the upper critical magnetic field (H C2) at zero temperature: 4.0 T at 19.6 GPa and 4.8 T at 41.8 GPa (Fig. 2c). Note that the upper critical fields obtained at 19.6 GPa and 41.8GPa are lower than their corresponding Pauli paramagnetic limits (10.3 T and 14.8T, respectively), suggesting that the nature of the pressure-induced superconducting state may differ from that of the initial superconducting state.To investigate whether the observed reemergence of superconductivity in pressurized K2Mo3As3 is associated with the pressure-induced crystal structure phase transition, we performed in-situ high pressure XRD measurements. The XRD patterns collected at different pressures are shown in Fig. 3. No structure phase transition is observed under pressure up to 51.6 GPa. And all peaks shift to higher angle due to the shrinkage of the lattice, except for the (002) peak. It is found that the (002) peak, which is realted to the parameter c, shifts toward to the lower angle starting at 8.8 GPa. Upon further compression, it becomes more pronounced. We propose that the left shift of the (002) peak may be a consequence of the pressure-induced elongation of the polycrystalline wire-like samples (the direction of the wire length is the c-axis of the K2Mo3As3 crystal lattice) due to their preferred orientation under pressure (see the right panel of Fig. 3). At higher pressure, the wire-like samples aline themselves perpendicular to the pressure direction applied.We summarise our results in Fig. 4a.The pressure-T c phase diagram clearly reveals three distinct superconducting regions: the initial superconducting state (SC-I), intermediary non-superconducting state (NSC) and the pressure-induced superconducting state (SC-II). In the SC-I region between 1 bar and 8.7 GPa, T c issuppressed with applied pressure, and not detectable above 8.7 GPa. In the SC-II region, T c increases with pressure and reaches the maximum (8.1 K) at 30 GPa. Upon further compression, T c shows slow a slight decline. This is the first observation of reemerging superconductivity in one-dimensional superconductors, to the best of our knowledge.We extract the lattice parameters and volume as a function of pressure, and summarise these results in Fig. 4b. It is found that the lattice constant a displays a decrease monotonously with pressure, while the lattice constant c shows a complicated relation with pressure applied. In the SC-I region, the parameter c shrinks upon increasing pressure, but it unusually expands in the NSC region. At the pressure of 18.2 GPa, the superconductivity reemerges and the lattice constant a and c decrease simultaneously with pressure again as what is seen in the SC-I region, implying that the pressure-induced elongation effect on the wire-like sample is satuated. The pressure dependence of the volume for K2Mo3As3 is shown in the inset of the Fig. 4b, displaying that the sample volume remains almost unchanged due to the increase of parameter c and the decrease of parameter a concurrently with elevating pressure in the NSC region. The strong correlation between the lattice parameters and the superconductivity in pressurized K2Mo3As3 suggests that the remarkable change of parameter c may paly an important role for the development of the SC-II state.To understand the underlying correlation between T c and the electronic state in K2Mo3As3 further, we performed the first-principles calculations on its electronic structure, based on our XRD results, by using the projector-augmented wave (PAW) method (see the Supplemental Material [29]). We find that the percentage of the density of states (P-DOS) at Fermi level for K2Mo3As3 is dominated by the electrons from the d xy and d x2-y2 orbitals in the pressure range investigated, with a secondary contribution from the d z2,p x and p y orbitals, and the P-DOSs of the p z, d xz, d yz and sorbitals are relatively small (see the Supplemental Material [29]). We note that, in the NSC and SC-II regions, the P-DOSs of the d xy, and d x2-y2orbitals decrease continuously with elevating pressure over the experimental range investigated, however, the change trend of the P-DOSs contributed by the d z2 and the p x as well as the p y orbitals displays differently. In the NSC region, the P-DOS of the d z2 orbital exibits a remarkable increase, while that of the p orbitals shows a slow decline (Fig. 4c). As the P-DOSs of the d z2 orbital and p orbitals reach a maximum and minimum respectively, SC-II state appears. Note that the T c value of the SC-II state increases upon compression in the pressure range of 18.2 GPa – 27 GPa, just where the P-DOS of the d z2 orbital displays a decrease again. Meanwhile, the P-DOSs of the p x and p y orbitals appear an increase in the same pressure range. Further compression from 27 GPa to 40 GPa, T c of the SC-II state stays almost constant, and the corresponding P-DOSs of the d z2 and p orbitals show a small change (Fig. 4c). These results suggest that the emergence of the SC-II state in K2Mo3As3 and its T c change with pressure are the consequence of the interplay among the different orbital electrons.In conclusion, the pressure-induced reemergence of the superconductivity is observed for the first time in the qausi-one-demensional superconductor K2Mo3As3. An intimate correlation between T c’s of the ambient-pressure and high-pressure superconducting states, lattice parameters and the density of state contributed by d z2, p x and p y orbitals have been revealed. We find that the initial superconducting state (SC-I) is suppressed by pressure at 8.7 GPa, and then an intermediary non-superconducting (NSC) state sets in and stabilizes up to 18 GPa. Subsequently, a new superconduting state (SC-II) emerges and prevails up to 47.4 GPa. Our synchrotron x-ray diffraction results indicats that the reemergence of superconductivity is not associated with anycrystal structure phase transition. In combination of theoretical calculations on the band strcture, our results suggest that the appearance of the SC-II state found in this material is a consenquence of the dramatic interplay among different orbital electrons due to the pressure-induced lattice change. We hope that the results found in this study will shed new light on understanding the correlation among superconductivity, electronic and lattice structures in unconventional quasi-one dimentional superconductors.AcknowledgementsWe thank Prof. V. A. Sidorov for useful discussions. The work was supported by the National Key Research and Development Program of China (Grant No. 2017YFA0302900, 2016YFA0300300 and 2017YFA0303103), the NSF of China (Grants No. U2032214, 12004419 and 12074414) and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB25000000). J. G. is grateful for support from the Youth Innovation Promotion Association of the CAS (2019008).*contributed equally to this work.†To whom correspondence may be addressed. Email: llsun@Reference[1].J. G. Bednorz and K. A. Müller, Possible high T c superconductivity in the Ba-La-Cu-O system, Z. Phys. B 64, 189 (1986).[2].M. K. Wu, J. R. Ashburn, C. J. Torng, P. H. Hor, R. L. Meng, L. Gao, Z. J. 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[29].See the supplementary material for electronic structure calculations; also see Refs.[30-36][30].P. E. Blöchl, Phys. Rev. B 50, 17953 (1994).[31].G. Kresse and D. Joubert, Phys. Rev. B 59, 1758 (1999).[32].G. Kresse and J. Hafner, Phys. Rev. B 47, 558 (1993).[33].G. Kresse and J. Furthmüller, Comput. Mater. Sci. 6, 15 (1996).[34].G. Kresse and J. Furthmüller, Phys. Rev. B 54, 11169 (1996).[35].J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 77, 3865 (1996).[36].H. J. Monkhorst and J. Pack, Phys. Rev. B 13, 5188 (1976).Fig. 1 (a) Resistance as a function of temperature for quausi-one-dimensional superconductor K2Mo3As3 at ambient pressure and its polycrystallined-sample’s image taken by a scanning electron microscope (inset). (b)-(d) Temperature dependence of the resistance in the pressure range of 1.2 GPa -8.7 GPa, 8.7-18.2 GPa, and 18.2-47.4 GPa, respectively. The insets of figure (b) and (d) display enlarged views of the the resistance in the low temperature regime.Fig. 2 Temperature dependence of resistance under different magnetic fields for K2Mo3As3measured at 19.6 GPa (a) and 41.8 GPa (b), respectively. (c) Plot of superconducting transition temperature T c versus critical field (H C2) for K2Mo3As3 at 19.6 GPa and 41.8 GPa, respectively. The dished lines represent the Ginzburg-Landau (GL) fits to the data of H C2.Fig. 3 X-ray diffraction patterns collected in the pressure range of 3.8 – 51.6 GPa for K2Mo3As3. The right panel schematically shows the evolution of the preferred orientation of the wire-like samples under pressures. SC-I and SC-II stand for the ambient-pressure superconducting state and the reemergence supercnducting states, respectively. NSC represents non-superconducting state.Fig 4 Superconductivity, crystal and electronic structure information for the qausi-one-dementional superconductor K2Mo3As3. (a) Pressure-Temperature phase diagram. (b) Pressure dependence of lattice parameters and volume (see inset). (c) Plots ofpercentage of the density of state (P-DOS) contrinuted by the d z2, p x and p y orbitals versus pressure.。

Current-Induced Superconductor-Insulator Transition in Granular High-T_c Superconductors

a r X i v :c o n d -m a t /0108311v 1 [c o n d -m a t .s u p r -c o n ] 20 A u g 2001CURRENT-INDUCED SUPERCONDUCTOR-INSULATOR TRANSITION INGRANULAR HIGH-T c SUPERCONDUCTORSY.Kopelevich*,C.A.M.dos Santos**,S.Moehlecke*,and A.J.S.Machado**(*)Instituto de F ´isica ”Gleb Wataghin”,Universidade Estadual de Campinas,Unicamp 13083-970,Campinas,S˜a o Paulo,Brasil(**)Departamento de Engenharia de Materiais,FAENQUIL,12600-000,Lorena,S˜a o Paulo,BrasilI.INTRODUCTIONThe occurrence of either superconducting or insulatingstate in a zero-temperature limit (T →0)under variation of system parameters such as,for instance,microscopic disorder in homogeneous thin ﬁlms [1–5]or charging en-ergy/Josephson energy ratio in granular superconductors [6,7],is one of the fundamental problems in the condensed matter physics which continuously attracts an intense re-search interest.It has also been shown both theoretically [8]and experimentally that the superconductor-insulator transition in two-dimensional (2D)superconductors can be tuned by applied magnetic ﬁeld.The ﬁeld-tuned superconductor-insulator transition has been measured in amorphous [5,9–11]and granular [12]thin ﬁlms,fabri-cated 2D Josephson-junction arrays [13,14],and bulk lay-ered quasi-2D superconductors such as high-T c cuprates [15,16].On the other hand,in granular superconductors both applied magnetic ﬁeld and electrical current aﬀect the Josephson coupling between grains [17–19].Besides,a zero-temperature current-driven dynamic transition from a vortex glass to a homogeneous ﬂow of the vortex mat-ter is expected to occur in disordered Josephson junc-tion arrays [20],suggesting the intriguing possibility of a current-induced superconductor-insulator transition,analogous to the ﬁeld-tuned transition [21].In this paper we report a systematic study of electrical current eﬀects on the superconducting properties of gran-ular high-T c superconductors.The here presented results demonstrate the occurrence of superconductor-insulator quantum phase transition driven by the applied electri-cal current,and provide evidence that the dynamics of Josephson intergranular vortices plays a crucial role in this phenomenon.II.SAMPLES AND EXPERIMENTAL DETAILSPolycrystalline single phase Y 1−x Pr x Ba 2Cu 3O 7−δsamples were prepared using a solid state reaction method with a route similar as described in [22]and char-acterized by means of x-ray powder diﬀractometry,andoptical and scanning electron microscopy.The analysis showed that the samples are granular materials consist-ing of grains with an average size d ∼5µm.The su-perconducting transition was measured both resistively and with a SQUID magnetometer MPMS5(Quantum Design).Electrical transport dc measurements in ap-plied magnetic ﬁeld H ≤100Oe,produced by a cop-per solenoid,were performed using standard four-probe technique with low-resistance (<1Ω)sputtered gold con-tacts.No heating eﬀects due to current were observed for I ≤100mA,our largest measuring current.In order to eliminate thermoelectric eﬀects,the measurements were performed inverting the applied current.Below we present the results of measurements per-formed on Y 1−x Pr x Ba 2Cu 3O 7−δsample with x =0.45close to the critical Pr concentration x c ≈0.57above which superconductivity has not been detected [22].The sample superconducting transition temperature (onset)T c 0=33K,the resistivity at the superconducting tran-sition ρN (T c 0)=20mΩcm,and dimensions l x w x t =12.6x 1.94x 1.24mm 3.III.RESULTS AND DISCUSSIONFigures 1–4present the resistance vs.temperature data obtained in a vicinity of T c 0=33K for various applied currents and magnetic ﬁelds.As Figs.1–4il-lustrate,the superconducting transition temperature on-set T c 0is both current-and ﬁeld-independent.On the other hand,the zero-resistance superconducting state is destroyed by the application of both the electrical current and magnetic ﬁeld.The superconducting order parameter Ψ=Ψ0e iφhas two components;a magnitude Ψ0and a phase φ.Be-cause T c 0(and hence Ψ0)remains unchanged,the low-temperature ﬁnite resistance in our sample originates from thermal and/or quantum ﬂuctuations in the phase locking.In the context of granular superconductors,T c 0can be identiﬁed with the transition temperature of indi-vidual grains,and the phase ﬂuctuations –with ﬂuctuat-ing Josephson currents between grains.In the absence of external ﬁeld,the critical current is that corresponding to a vortex creation and its motion,neglecting pinning.However,in granular superconductors with a very weak coupling between grains,the Earth’s magnetic ﬁeld H E ∼0.5Oe (which has not been shielded in the experiments)can easily penetrate the sample.Then,the criticalvarious at the at no variousOe. various Oe.variousOe.fromtemperatures and at no appliedﬁeld.As can be seen from Fig.5, the V(I)dependencies can be very well described by the equationV=c(T,H)(I−I th(T,H))n(T,H),(1) where I th(T,H)is the threshold current.Thus,at T=4.6K,I th=5mA and the corresponding current density(I th/cross section of the sample)j th=0.21A/cm2.T=13ﬁtting3(T=(T=8=8K);13K).ﬁeldH c 1J ∼8π2j c 0λL /c ∼0.2mOe,taking the maximum Josephson current densityj c 0∼10j th [23,26]and the typ-ical value of the intragranular London penetration depth λL ∼0.1µm (<<d).The obtained value of H c 1J is much smaller than the Earth’s magnetic ﬁeld,indeed,i.e.our sample is deeply in the mixed state.Below the threshold current I th (H,T)the vortex mo-tion is strongly suppressed or zero.The I-V charac-teristics described by the Eq.(1)are expected in the regime where the interaction between vortices and the pinning potential dominates the vortex-vortex interac-tion [20,27–29].As the applied current increases,the V(I)curves ap-proach a linear regime of ﬂux ﬂow where the diﬀerential resistance R d =dV/dI is current-independent,see Fig.6.Inset in Fig.6exempliﬁes V(I)measured at T =13K and demonstrates that at large enough currents the V(I)can be ﬁtted by the equationV (I )=R ff (I −I cf ).(2)Here R ff is the ﬂux-ﬂow resistance and I cf is the so-called dynamical critical current.In this high-current regime vortices move coherently,only weakly interacting with the pinning potential.at no K (△),13K;0.215performed at various applied ﬁelds revealed that I d (H)is a decreasing function of ﬁeld.Such a crossing has also been measured in Mo 77Ge 23ﬁlms [30]and reproduced in numerical simulations [31]which show that the pinned fraction of vortices rapidly decreases for I >I d (H).Figure 7presents typical resistance hysteresis loops R(H)measured at T =4.2K for various currents.These measurements were performed after cooling the sample from T >T c 0to the target temperature in a zero ap-plied ﬁeld.As shown in Fig.7,the resistance R cor-responding to the increasing |H |branch is larger than that corresponding to the decreasing |H |branch result-ing in “clockwise”R(H)hysteresis loops.Previous stud-ies [32–34]showed that the “clockwise”R(H)hystere-sis loops are essentially related to the granular sample structure where the resistance is determined by the mo-tion of Josephson intergranular vortices.In increasing magnetic ﬁeld larger than the ﬁrst critical ﬁeld of the grains (H >H c 1g ),the pinning prevents Abrikosov vor-tices from entering the grains,and ﬂux lines (Joseph-son vortices)are concentrated between grains leading to the intergrain ﬁeld higher than the external applied ﬁeld.When the applied ﬁeld is decreased,the pinning prevents Abrikosov vortices being expelled from the grains result-ing in a lower density of Josephson intergrain vortices as compared to that in the increasing ﬁeld.Thus,the data of Fig.7provide an unambiguous evidence that the resistance in our sample is governed by the motion of intergranular Josephson vortices in both low-and high-current limits.and I =60mA,demonstrating that the sample resistance is governed by the motion of intergranular Josephson vortices;arrows indicate the magnetic ﬁeld direction in the measure-ments.We note further that the resistance R(T)=V(T)/I in the low-temperature limit reveals a crossover from the metallic-like (dR/dT >0)to the insulating-like (dR/dT <0)behavior as the applied current isincreased,see Figs.1-4.The results presented in Figs.1-4indi-cate also the existence of a ﬁeld-dependent current I c (H),separating the metallic-like (I <I c (H))and insulating-like (I >I c (H))resistance curves,at which the resis-tance is temperature-independent.The occurrence of the temperature-independent resistance R c =(V/I)|I c can clearly be seen in Fig.8where a crossing of current-voltage I-V isotherms at I c (H)measured for two applied ﬁelds is shown.The inset in Fig.8depicts I c (H)and I d (H)which illustrates that for a given ﬁeld I c (H)>I d (H).In other words,the crossing of I-V curves takes place in the regime where the interaction between Joseph-son vortices dominates that with the pinning potential.in ).Inset to to the zero-resistance (R =0)superconducting state.With in-creasing vortex density and above some critical ﬁeld H c vortices delocalize and Bose condense,leading to the in-sulating state.The theory predicts a ﬁnite-temperature scaling law [2,3,8]which allows for experimental testing of the zero-temperature superconductor-insulator transition.It is assumed in this analysis that a sample is superconduc-tor or insulator at T =0when dR/dT >0or dR/dT <0,respectively.Besides,because the magnitude of the superconducting order parameter Ψ0(T c 0)remains unchanged on each grain as the intergranular resistance R(T,H,I)undergoes the transition from metallic-like to insulating-like behavior,the hard-core boson model [2,3,8]should be a good approximation in our analysisof the superconductor-insulator transition driven by the applied current.The resistance in the critical regime of the quantum transition is given by the equationR (δ,T )=R c f (|δ|/T 1/zν),(3)where R c is the resistance at the transition,f(|δ|/T 1/zν)is the scaling function such that f(0)=1,z and νare critical exponents,and δis the deviation of a variable parameter from its critical value.Assuming δ=I -I c (δ=H -H c in the case of a ﬁeld-tuned transition)we plotted in Figs.9-11,R =V/I vs.|δ|/T 1/αfor three applied ﬁelds.In each case,the exponent αwas obtained from log-log plots of (dR/dI)|I c vs.T −1.The expected collapse of the resistance data onto two branches distin-guishing the I <I c from the I >I c data is very clear in Figs.9-11.scaling =16.26.7K scaling mA,(△),T the re-sults presented in Figs.9-11should be considered as empirical ones,the very good scalingﬁt strongly suggests the occurrence of a zero-temperature current-induced superconductor-insulator transition.Notably,the here found exponentsαagree nicely with most of the data obtained in the scaling analysis of theﬁeld-tuned transi-tion[5,9–16].scalingmA,α),T= In conclusion,we would like to emphasize that the here studied superconductor-insulator transition driven by the electrical current is essentially related to the dynamics of Josephson intergranular vortices.Actually,as the above results demonstrate,the crossing of I-V characteristics takes place in theﬂuxﬂow regime.We stress that the crossover current I c(H)is smaller than the maximum su-percurrent I0=(2e/ )E J(E J is the Josephson coupling energy)that the Josephson junctions can support.In other words,both tunneling Cooper pairs and moving Josephson vortices are present at the I c(H)which play a dual role as discussed in the context of theﬁeld-tuned transition[8].A self-consistent analysis would require the existence of zero-temperature“depinning”transition in the Joseph-son vortex matter driven by the applied current.The occurrence of such a transition in disordered Josephson junction arrays has theoretically been predicted,indeed [20].All these indicate that the current-induced superconductor-insulator transition can be considered as the dynamical counterpart of the magnetic-ﬁeld-tuned transition.Finally,we point out that similar results were obtained on Y1−x Pr x Ba2Cu3O7−δ(x=0.5)and Bi2Sr2Ca1−x Pr x Cu2O8+δ(x=0.54)granular supercon-ductors.V.ACKNOWLEDGEMENTSThe authors would like to thank Enzo Granato for the fruitful discussions.This study was supported by FAPESP and CNPq Brazilian science agencies.New Superconductors”in H.Ehrenreich and D.Turnbull (eds.)Solid State Phys.42(1989)91.[26]C.J.Lobb,D.W.Abraham,and M.Tinkham,Phys.Rev.B27(1983)150.[27]P.Berghuis and P.H.Kes,Phys.Rev.B47(1993)262.[28]S.Bhattacharya and M.J.Higgins,Phys.Rev.Lett.70(1993)2617.[29]Y.Enomoto,K.Katsumi,and S.Maekawa,Physica C215(1993)51.[30]M.C.Hellerqvist,D.Ephron,W.R.White,M.R.Beasly,and A.Kapitulnik,Phys.Rev.Lett.76(1996)4022;M.C.Hellerqvist and A.Kapitulnik,Phys.Rev.B56(1997)5521.[31]S.Ryu,M.Hellerqvist,S.Doniach,A.Kapitulnik,andD.Stroud,Phys.Rev.Lett.77(1996)5114.[32]Y.Kopelevich,V.V.Lemanov,and V.V.Makarov,Sov.Phys.Solid State32(1990)2095;V.V.Makarov and Y.Kopelevich,Phys.Rev.B54(1996)84.[33]L.Ji,M.S.Rzchowski,N.Anand,and M.Tinkham,Phys.Rev.B47(1993)470.[34]S.Li,M.Fistul,J.Deak,P.Metcalf,and M.McElfresh,Phys.Rev.B52(1995)747.。

作文未来超导技术450字的

作文未来超导技术450字的英文回答：Superconducting technology is poised to revolutionize various industries and sectors in the future. With itsability to conduct electricity with zero resistance, superconductors have the potential to greatly enhanceenergy efficiency, transportation systems, and even medical applications.In terms of energy efficiency, superconductingmaterials can significantly reduce energy loss during transmission and distribution. This means that electricity can be transmitted over long distances without any loss of power, leading to more efficient and cost-effective energy systems. This technology can also be applied to power grids, allowing for better management and stability.In the transportation sector, superconductors can revolutionize the way we travel. Magnetic levitation(maglev) trains, which use superconducting magnets to float above the tracks, can achieve incredible speeds and efficiency. This technology has the potential to transform long-distance travel, making it faster, safer, and more environmentally friendly.Furthermore, superconducting technology can greatly benefit the medical field. Magnetic resonance imaging (MRI) machines, which use superconducting magnets, provide detailed and accurate images of the human body. This technology has revolutionized medical diagnosis and treatment, allowing for earlier detection of diseases and more precise surgical procedures.In conclusion, the future of superconducting technology is bright. Its potential to enhance energy efficiency, revolutionize transportation, and improve medical applications cannot be overstated. As research and development in this field continue to advance, we can expect to see even more innovative and practical applications of superconductors in the near future.中文回答：超导技术有望在未来革新各个行业和领域。

Two gaps make a high-temperature superconductor

IOP P UBLISHING R EPORTS ON P ROGRESS IN P HYSICS Rep.Prog.Phys.71(2008)062501(9pp)doi:10.1088/0034-4885/71/6/062501Two gaps make a high-temperature superconductor?S H¨ufner1,2,M A Hossain1,2,A Damascelli1,2and G A Sawatzky1,21AMPEL,University of British Columbia,Vancouver,British Columbia,V6T1Z4,Canada2Department of Physics and Astronomy,University of British Columbia,Vancouver,British Columbia,V6T1Z1,CanadaReceived27February2008,inﬁnal form2April2008Published2May2008Online at /RoPP/71/062501AbstractOne of the keys to the high-temperature superconductivity puzzle is the identiﬁcation of theenergy scales associated with the emergence of a coherent condensate of superconductingelectron pairs.These might provide a measure of the pairing strength and of the coherence ofthe superﬂuid,and ultimately reveal the nature of the elusive pairing mechanism in thesuperconducting cuprates.To this end,a great deal of effort has been devoted to investigatingthe connection between the superconducting transition temperature T c and the normal-statepseudogap crossover temperature T∗.Here we present a review of a large body ofexperimental data which suggests a coexisting two-gap scenario,i.e.superconducting gap andpseudogap,over the whole superconducting dome.We focus on spectroscopic data fromcuprate systems characterized by T maxc ∼95K,such as Bi2Sr2CaCu2O8+δ,YBa2Cu3O7−δ,Tl2Ba2CuO6+δand HgBa2CuO4+δ,with particular emphasis on the Bi-compound which has been the most extensively studied with single-particle spectroscopies.(Someﬁgures in this article are in colour only in the electronic version)This article was invited by Professor L Greene.Contents1.Introduction12.Emerging phenomenology32.1.Angle-resolved photoemission42.2.Tunneling52.3.Raman scattering52.4.Inelastic neutron scattering52.5.Heat conductivity63.Outlook and conclusion6 Acknowledgments6 References71.IntroductionSince their discovery[1],the copper-oxide high-T c superconductors(HTSCs)have become one of the most investigated class of solids[2–24].However,despite the intense theoretical and experimental scrutiny,an understanding of the mechanism that leads to superconductivity is still lacking.At the very basic level,what distinguishes the cuprates from the conventional superconductors is the fact that they are doped materials,the highly atomic-like Cu 3d orbitals give rise to strong electron correlations(e.g. the undoped parent compounds are antiferromagnetic Mott–Hubbard-like insulators),and the superconducting elements are weakly-coupled two-dimensional layers(i.e.the celebrated square CuO2planes).Among the properties that are unique to this class of superconducting materials,in addition to the unprecedented high superconducting T c,the normal-state gap or pseudogap is perhaps the most noteworthy.The pseudogap wasﬁrst detected in the temperature dependence of the spin-lattice relaxation and Knight shift in nuclear magnetic resonance and magnetic susceptibility studies[25].The Knight shift is proportional to the density of states at the Fermi energy;a gradual depletion was observed below a crossover temperature T∗,revealing the opening of the pseudogap well above T c on the underdoped side of the HTSC phase diagram(ﬁgure1).As the estimates based on thermodynamicx (c)Tx (a)x(b)T* T cT*T cT*T cFigure1.Various scenarios for the interplay of pseudogap(blue dashed line)and superconductivity(red solid line)in thetemperature-doping phase diagram of the HTSCs.While in(a)the pseudogap merges gradually with the superconducting gap in the strongly overdoped region,in(b)and(c)the pseudogap lines intersect the superconducting dome at about optimal doping(i.e.maximum T c).In most descriptions,the pseudogap line is identiﬁed with a crossover with a characteristic temperature T∗rather than a phase transition;while at all dopings T∗>T c in(a),beyond optimal doping T∗<T c in(b)and T∗does not even exist in(c).Adapted from[12].quantities are less direct than in spectroscopy we,in the course of this review,concentrate mainly on spectroscopic results; more information on other techniques can be found in the literature[5].As established by a number of spectroscopic probes, primarily angle-resolved photoemission spectroscopy,[26,27] the pseudogap manifests itself as a suppression of the normal-state electronic density of states at E F exhibiting a momentum dependence reminiscent of a d x2−y2functional form.For hole-doped cuprates,it is largest at Fermi momenta close to the antinodal region in the Brillouin zone—i.e.around (π,0)—and vanishes along the nodal direction—i.e.the(0,0) to the(π,π)line.Note however that,strictly speaking, photoemission and tunneling probe a suppression of spectral weight in the single-particle spectral function,rather than directly of density of states;to address this distinction,which is fundamental in many-body systems and will not be further discussed here,it would be very interesting to investigate the quantitative correspondence between nuclear magnetic resonance and single-particle spectroscopy results.Also,no phase information is available for the pseudogap since,unlike the case of optimally and overdoped HTSCs[28],no phase-sensitive experiments have been reported for the underdoped regime where T∗ T c.As for the doping dependence,the pseudogap T∗is much larger than the superconducting T c in underdoped samples,it smoothly decreases upon increasing the doping,and seems to merge with T c in the overdoped regime,eventually disappearing together with superconductivity at doping levels larger than x∼0.27[5–24].In order to elaborate on the connection between pseudogap and high-T c superconductivity,or in other words between the two energy scales E pg and E sc identiﬁed by T∗and T c,respectively,let us start by recalling that in conventional superconductors the onset of superconductivity is accompanied by the opening of a gap at the chemical potential in the one-electron density of states. According to the Bardeen–Cooper–Schrieffer(BCS)theory of superconductivity[29],the gap energy provides a direct measure of the binding energy of the two electrons forming a Cooper pair(the two-particle bosonic entity that characterizes the superconducting state).It therefore came as a great surprise that a gap,i.e.the pseudogap,was observed in the HTSCs not only in the superconducting state as expected from BCS, but also well above T c.Because of these properties and the hope it might reveal the mechanism for high-temperature superconductivity,the pseudogap phenomenon has been very intensely investigated.However,no general consensus has been reached yet on its origin,its role in the onset of superconductivity itself,and not even on its evolution across the HTSC phase diagram.As discussed in three recent papers on the subject [12,15,17],and here summarized inﬁgure1,three different phase diagrams are usually considered with respect to the pseudogap line.While Millis[15]opts for a diagram like the one inﬁgure1(a),Cho[17]prefers a situation where the pseudogap line meets the superconducting dome at x 0.16(ﬁgures1(b)and(c));Norman et al[12]provide a comprehensive discussion of the three different possibilities. One can summarize some of the key questions surrounding the pseudogap phenomenon and its relevance to high-temperature superconductivity as follows[12,15,17]:1.Which is the correct phase diagram with respect to thepseudogap line?2.Does the pseudogap connect to the insulator quasiparticlespectrum?3.Is the pseudogap the result of some one-particle bandstructure effect?4.Or,alternatively,is it a signature of a two-particle pairinginteraction?5.Is there a true order parameter deﬁning the existence of apseudogap phase?6.Do the pseudogap and a separate superconducting gapcoexist below T c?7.Is the pseudogap a necessary ingredient for high-T csuperconductivity?In this review we revisit some of these questions,with speciﬁc emphasis on the one-versus two-gap debate.Recently,this latter aspect of the HTSCs has been discussed in great detail by Goss Levi[30],in particular based on scanning-tunneling microscopy data from various groups[31–33].Here we expand this discussion to include the plethora of experimental results available from a wide variety of techniques.We0.050.100.150.200.250408012016050100150E n e r g y (m e V )Hole doping (x)T c (K )Figure 2.Pseudogap (E pg =2 pg )and superconducting (E sc ∼5k B T c )energy scales for a number of HTSCs with T max c ∼95K(Bi2212,Y123,Tl2201and Hg1201).The datapoints were obtained,as a function of hole doping x ,by angle-resolved photoemission spectroscopy (ARPES),tunneling (STM,SIN,SIS),Andreev reﬂection (AR),Raman scattering (RS)and heat conductivity (HC).On the same plot we are also including the energy r of the magnetic resonance mode measured by inelastic neutron scattering (INS),which we identify with E sc because of the striking quantitative correspondence as a function of T c .The data fall on two universal curvesgiven by E pg =E max pg (0.27−x)/0.22and E sc =E max sc [1−82.6(0.16−x)2],with E maxpg =E pg (x =0.05)=152±8meV and E maxsc =E sc (x =0.16)=42±2meV (the statistical errors refer to the ﬁt of the selected datapoints;however,the spread of all available data would be more appropriately described by ±20and ±10meV ,respectively).show that one fundamental and robust conclusion can be drawn:the HTSC phase diagram is dominated by two energy scales,the superconducting transition temperature T c and the pseudogap crossover temperature T ∗,which converge to the very same critical point at the end of the superconducting dome.Establishing whether this phenomenology can be conclusively described in terms of a coexisting two-gap scenario,and what the precise nature of the gaps would be,will require a more deﬁnite understanding of the quantities measured by the various probes.2.Emerging phenomenologyThe literature on the HTSC superconducting gap and/or pseudogap is very extensive and still growing.In this situation it seems interesting to go over the largest number of data obtained from as many experimental techniques as possible,and look for any possible systematic behavior that could be identiﬁed.This is the primary goal of this focused review.We want to emphasize right from the start that we are not aiming at providing exact quantitative estimates of superconducting and pseudogap energy scales for any speciﬁc compound or any given doping.Rather,we want to identify the general phenomenological picture emerging from the whole body of available experimental data [5,9,13,16,18,34–72].We consider some of the most direct probes of low-energy,electronic excitations and spectral gaps,such as angle-resolved photoemission (ARPES),scanning-tunneling microscopy (STM),superconductor/insulator/normal-metal(SIN)and superconductor/insulator/superconductor (SIS)tunneling,Andreev reﬂection tunneling (AR)and Raman scattering (RS),as well as less conventional probes such as heat conductivity (HC)and inelastic neutron scattering (INS).The emphasis in this review is on spectroscopic data because of their more direct interpretative signiﬁcance;however,these will be checked against thermodynamic/transport data whenever possible.With respect to the spectroscopic data,it is important to differentiate between single-particle probes such as ARPES and STM,which directly measure the one-electron excitation energy with respect to the chemical potential (on both side of E F in STM),and two-particle probes such as Raman and inelastic neutron scattering,which instead provide information on the particle-hole excitation energy 2 .Note that the values reported here are those for the ‘full gap’2 (associated with either E sc or E pg ),while frequently only half the gap is given for instance in the ARPES literature.In doing so one implicitly assumes that the chemical potential lies half-way between the lowest-energy single-electron removal and addition states;this might not necessarily be correct but appears to be supported by the direct comparison between ARPES and STM/Raman results.A more detailed discussion of the quantities measured by the different experiments and their interpretation is provided in the following subsections.Here we would like to point out that studies of B 2g and B 1g Raman intensity [19,40,52],heat conductivity of nodal quasiparticles [70,71]and neutron magnetic resonance energy r [42]do show remarkable agreement with superconducting or pseudogap energy scales as inferred by single-particleTable1.Pseudogap E pg and superconducting E sc energy scales (2 )as inferred,for optimally doped Bi2212(T c∼90–95K),from different techniques and experiments.Abbreviations are given in the main text,while the original references are listed.Experiment Energy meV ReferencesARPES—(π,0)peak E pg80[34,35]Tunneling—STM…70[18,36]Tunneling—SIN…85[37]Tunneling—SIS…75[38,39]Raman—B1g…65[40]Electrodynamics…80[5,41]Neutron—(π,π) r E sc40[42]Raman—B2g…45[40]Andreev…45[43]SIS—dip…40[39]probes,or with the doping dependence of T c itself.Thus they provide,in our opinion,an additional estimate of E sc and E pg energy scales.As for the choice of the speciﬁc compounds to include in our analysis,we decided to focus on those HTSCs exhibiting a similar value of the maximum superconductingtransition temperature T maxc ,as achieved at optimal doping,so that the data could be quantitatively compared without any rescaling.We have therefore selected Bi2Sr2CaCu2O8+δ(Bi2212),YBa2Cu3O7−δ(Y123),Tl2Ba2CuO6+δ(Tl2201) and HgBa2CuO4+δ(Hg1201),which have been extensivelyinvestigated and are all characterized by T maxc ∼95K[73](with particular emphasis on Bi2212,for which the most extensive set of single-particle spectroscopy data is available). It should also be noted that while Bi2212and Y123are ‘bilayer’systems,i.e.their crystal structure contains as a key structural element sets of two adjacent CuO2layers, Tl2201and Hg1201are structurally simpler single CuO2-layer materials.Therefore,this choice of compounds ensures that our conclusions are generic to all HTSCs with a similar T c, independent of the number of CuO2layers.A compilation of experimental results for the magnitude of pseudogap(E pg=2 pg)and superconducting(E sc∼5kB T c) energy scales,as a function of carrier doping x,is presented inﬁgure2(only some representative datapoints are shown,so as not to overload theﬁgure;similar compilations were also obtained by a number of other authors)[5,9,13,16,42,43,52, 57,60,70,74,75].The data for these HTSCs with comparableT max c ∼95K fall on two universal curves:a straight linefor the pseudogap energy E pg=2 pg and a parabola for the superconducting energy scale E sc∼5k B T c.The two curves converge to the same x∼0.27critical point at the end of the superconducting dome,similarly to the cartoon of ﬁgure1(a).In order to summarize the situation with respect to quantitative estimates of E pg and E sc,we have listed in table1the values as determined by the different experimental techniques on optimally doped Bi2212(with T c ranging from 90to95K).While one obtains from this compilation the average values of E pg 76meV and E sc 41meV at optimal doping,the numbers do scatter considerably.Note also that these numbers differ slightly from those given in relation to the parabolic and straight lines inﬁgure2(e.g.E maxsc= 42meV)because the latter were inferred from aﬁtting of superconducting and pseudogap data over the whole doping range,while those in table1were deduced from results for optimally doped Bi2212only.It is also possible to plot the pseudogap E pg and superconducting E sc energy scales as estimated simultaneously in one single experiment on the very same sample.This is done inﬁgure3for Raman,tunneling and ARPES results from Bi2212and Hg1201,which provide evidence for the presence of two energy scales,or possibly two spectral gaps as we discuss in greater detail below,coexisting over the whole superconducting dome.2.1.Angle-resolved photoemissionThe most extensive investigation of excitation gaps in HTSCs has arguably been done by ARPES[9,10,26,27,34,35,54–66,76–80].This technique provides direct access to the one-electron removal spectrum of the many-body system;it allows,for instance in the case of a BCS superconductor[29], to measure the momentum dependence of the absolute value of the pairing amplitude2 via the excitation gap observed for single-electron removal energies,again assuming E F to be located half-way in the gap[9,10].This is the same in some tunneling experiments such as STM,which however do not provide direct momentum resolution but measure on both sides of E F[18].The gap magnitude is usually inferred from the ARPES spectra from along the normal-state Fermi surface in the antinodal region,where the d-wave gap is largest;it is estimated from the shift to high-binding energy of the quasiparticle spectral weight relative to the Fermi energy.With this approach only one gap is observed below a temperature scale that smoothly evolves from the so-called pseudogap temperature T∗in the underdoped regime,to the superconducting T c on the overdoped side.We identify this gap0.050.100.150.200.25408012016050100150Energy(meV)Hole doping (x)T c(K)Figure3.Pseudogap E pg and superconducting E sc energy scales (2 )as estimated,by a number of probes and for different compounds,in one single experiment on the very same sample. These data provide direct evidence for the simultaneous presenceof two energy scales,possibly two spectral gaps,coexisting in the superconducting state.The superconducting and pseudogap lines are deﬁned as inﬁgure2.with the pseudogap energy scale E pg=2 pg.This is also in agreement with recent investigations of the near-nodal ARPES spectra from single and double layer Bi-cuprates[57,76,77], which further previous studies of the underdoped cuprates’Fermi arc phenomenology[78–80].From the detailed momentum dependence of the excitation gap along the Fermi surface contour,and the different temperature trends observed in the nodal and antinodal regions,these studies suggest the coexistence of two distinct spectral gap components over the whole superconducting dome:superconducting gap and pseudogap,dominating the response in the nodal and antinodal regions,respectively,which would eventually collapse to one single energy scale in the very overdoped regime.2.2.TunnelingThe HTSCs have been investigated by a wide variety of tunneling techniques[13,18,36–39,44–51],such as SIN[38,51],SIS[37–39],STM[18,36,46],intrinsic tunneling[47–50]and Andreev reﬂection,which is also a tunneling experiment but involves two-particle rather than single-particle tunneling(in principle,very much like SIS) [13,43,72].All these techniques,with the exception of intrinsic tunneling3,are represented here either in theﬁgures or table.Similarly to what was discussed for ARPES at the antinodes,there are many STM studies that report a pseudogap E pg smoothly evolving into E sc upon overdoping[18,31]. In addition,a very recent temperature-dependent study of overdoped single-layer Bi-cuprate detected two coexisting,yet clearly distinct,energy scales in a single STM experiment[32]. In particular,while the pseudogap was clearly discernible in the differential conductance exhibiting the usual large spatial modulation,the evidence for a spatially uniform superconducting gap was obtained by normalizing the low-temperature spectra by those just above T c 15K.These values have not been included inﬁgures2and3because T c 95K;however,this study arguably provides the most direct evidence for the coexistence of two distinct excitation gaps in the HTSCs.One can regard Andreev reﬂection(pair creation in addition to a hole)as the inverse of a two-particle scattering experiment such as Raman or INS.A different view is also possible:SIN tunneling goes over to AR if the insulator layer gets thinner and thinner[13];thus a SIN tunneling,as also STM,should give the same result as AR.However while SIN and STM measure the pseudogap,AR appears to be sensitive to the superconducting energy scale E sc(ﬁgure2).We can only conjecture that this has to do with the tunneling mechanisms actually being different.3The most convincing tunneling results showing two coexisting gaps were actually obtained by intrinsic tunneling[47–50],in particular from Bi2Sr2CuO6+δ(Bi2201)[48].However,because this technique suffers from systematic problems[50],and one would anyway have to scale the Bi2201data because of the lower value of T c and in turn gap energy scales,these results were not included inﬁgures2or3.Since intrinsic tunneling is in principle a clean SIS experiment which measures pair energies through Josephson tunneling, a reﬁnement of the technique might provide an accurate estimate of both superconducting and pseudogap simultaneously,and is thus highly desirable.SIS tunneling experiments[39]ﬁnd E pg/E sc 1for Bi2212at all doping levels.There are,however,some open questions concerning the interpretation of the SIS experiments. This technique,which exploits Josephson tunneling,measures pair spectra;the magnitude of E pg can readily be obtained from the most pronounced features in the spectra[39].The signal related to E sc is seen as a‘sideband’on the E pg features;it does not seem obvious why,if the E sc signal did originate from a state of paired electrons,it would not show up more explicitly.2.3.Raman scatteringLight scattering measures a two-particle excitation spectrum providing direct insight into the total energy needed to break up a two-particle bound state or remove a pair from a condensate. Raman experiments can probe both superconducting and pseudogap energy scales,if one interprets the polarization dependent scattering intensity in terms of different momentum averages of the d-wave-like gap functions:one peaked at(π,0) in B1g geometry,and thus more sensitive to the larger E pg which dominates this region of momentum space;the other at(π/2,π/2)in B2g geometry,and provides an estimate of the slope of the gap function about the nodes,(1/¯h)(d /d k)|n, which is more sensitive to the arguably steeper functional dependence of E sc out of the nodes[19,40,52,53].One should note,however,that the signal is often riding on a high background,which might result in a considerable error and data scattering.At a more fundamental level,while the experiments in the antinodal geometry allow a straightforward determination of the gap magnitude E pg,the nodal results need a numerical analysis involving a normalization of the Raman response function over the whole Brillouin zone,a procedure based on a low-energy B2g sum rule(although also the B2g peak position leads to similar conclusions)[52].This is because a B2g Raman experiment is somewhat sensitive also to the gap in the antinodal direction,where it picks up,in particular,the contribution from the larger pseudogap.2.4.Inelastic neutron scatteringInelastic neutron scattering experiments have detected the so-called q=(π,π)resonant magnetic mode in all of the T c 95K HTSCs considered here[16].This resonance is proposed by some to be a truly collective magnetic mode that, much in the same way as phonons mediate superconductivity in the conventional BCS superconductors,might constitute the bosonic excitation mediating superconductivity in the HTSCs. The total measured intensity,however,amounts to only a small portion of what is expected based on the sum rule for the magnetic scattering from a spin1/2system[8,16,24, 42,68,69];this weakness of the magnetic response should be part of the considerations in the modeling of magnetic resonance mediated high-T c superconductivity.Alternatively, its detection below T c might be a mere consequence of the onset of superconductivity and of the corresponding suppression of quasiparticle scattering.Independently of the precise interpretation,the INS data reproduced inﬁgure2show that the magnetic resonance energy r tracks very closely, over the whole superconducting dome,the superconductingenergy scale E sc∼5k B T c(similar behavior is observed, in the underdoped regime,also for the spin-gap at the incommensurate momentum transfer(π,π±δ)[81]).Also remarkable is the correspondence between the energy of the magnetic resonance and that of the B2g Raman peak.Note that while the q=(π,π)momentum transfer observed for the magnetic resonance in INS is a key ingredient of most proposed HTSC descriptions,Raman scattering is a q=0probe.It seems that understanding the connection between Raman and INS might reveal very important clues.2.5.Heat conductivityHeat conductivity data from Y123and Tl2201fall onto the pseudogap line.This is a somewhat puzzling result because they have been measured at very low temperatures,well into the superconducting state,and should in principle provide a measure of both gaps together if these were indeed coexisting below T c.However,similarly to the B2g Raman scattering, these experiments are only sensitive to the slope of the gap function along the Fermi surface at the nodes,(1/¯h)(d /d k)|n; the gap itself is determined through an extrapolation procedure in which only one gap was assumed.The fact that the gap values,especially for Y123,come out on the high side of the pseudogap line may be an indication that an analysis with two coexisting gaps might be more appropriate.3.Outlook and conclusionThe data inﬁgures2and3demonstrate that there are two coexisting energy scales in the HTSCs:one associated with the superconducting T c and the other,as inferred primarily from the antinodal region properties,with the pseudogap T∗. The next most critical step is that of addressing the subtle questions concerning the nature of these energy scales and the signiﬁcance of the emerging two-gap phenomenology towards the development of a microscopic description of high-T c superconductivity.As for the pseudogap,which grows upon underdoping, it seems natural to seek a connection to the physics of the insulating parent compound.Indeed,it has been pointed out that this higher energy scale might smoothly evolve,upon underdoping,into the quasiparticle dispersion observed by ARPES in the undoped antiferromagnetic insulator[82,83]. At zero doping the dispersion and quasiparticle weight in the single-hole spectral function as seen by ARPES can be very well explained in terms of a self-consistent Born approximation[84],as well as in the diagrammatic quantum Monte Carlo[85]solution to the so-called t–t –t –J model.In this model,as in the experiment[82,83],the energy difference between the top of the valence band at(π/2,π/2)and the antinodal region at(π,0)is a gap due to the quasiparticle dispersion of about250±30meV.Note that this would be a single-particle gap .For the direct comparison with the pseudogap data inﬁgure2,we would have to consider 2 ∼500meV;this,however,is much larger than the x=0 extrapolated pseudogap value of186meV found from our analysis across the phase diagram.Thus there seems to be an important disconnection between theﬁnite doping pseudogapand the zero-doping quasiparticle dispersion.The fact that the pseudogap measured in ARPES and SINexperiments is only half the size of the gap in SIS,STM,B1gRaman and heat conductivity measurements,points to a pairinggap.So although the origin of the pseudogap atﬁnite dopingremains uncertain,we are of the opinion that it most likelyreﬂects a pairing energy of some sort.To this end,the trend inﬁgure2brings additional support to the picture discussed bymany authors that the reduction in the density of states at T∗isassociated with the formation of electron pairs,well above theonset of phase coherence taking place at T c(see,e.g.[86,87]).The pseudogap energy E pg=2 pg would then be the energy needed to break up a preformed pair.To conclusively addressthis point,it would be important to study very carefully thetemperature dependence of the(π,0)response below T c;anyfurther change with the onset of superconductivity,i.e.anincrease in E pg,would conﬁrm the two-particle pairing picture,while a lack thereof would suggest a one-particle band structureeffect as a more likely interpretation of the pseudogap.The lower energy scale connected to the superconductingT c(parabolic curve inﬁgure2and3)has already been proposedby many authors to be associated with the condensationenergy[86–89],as well as with the magnetic resonance inINS[90].One might think of it as the energy needed totake a pair of electrons out of the condensate;however,fora condensate of charged bosons,a description in terms of acollective excitation,such as a plasmon or roton,would bemore appropriate[24].The collective excitation energy wouldthen be related to the superﬂuid density and in turn to T c.In thissense,this excitation would truly be a two-particle process andshould not be measurable by single-particle spectroscopies.Also,if the present interpretation is correct,this excitationwould probe predominantly the charge-response of the system;however,there must be a coupling to the spin channel,so as tomake this process neutron active(yet not as intense as predictedby the sum rule for pure spin-1/2magnetic excitations,whichis consistent with the small spectral weight observed by INS).As discussed,one aspect that needs to be addressed to validatethese conjectures is the surprising correspondence betweenq=0and q=(π,π)excitations,as probed by Raman andINS,respectively.We are led to the conclusion that the coexistence of twoenergy scales is essential for high-T c superconductivity,withthe pseudogap reﬂecting the pairing strength and the other,always smaller than the pseudogap,the superconductingcondensation energy.This supports the proposals thatthe HTSCs cannot be considered as classical BCSsuperconductors,but rather are smoothly evolving from theBEC into the BCS regime[91–93],as carrier doping isincreased from the underdoped to the overdoped side of thephase diagram.AcknowledgmentsSH would like to thank the University of British Columbiafor its hospitality.Helpful discussions with W N Hardy,。

固_固接触界面热传输研究 2008

式表明, 热导率与平均自由程成正比。结合界面
厚度的分析, 界面层热导率是否如体材热导率一
样, 是一种本质属性, 值得深入细致地研究。因为
界面层内热载子的平均自由程会随界面层的几何
厚度不同而变化, 导致热导率也会发生变化, 所以
界面层热导率还取决于几何参数 ) ) ) 界面层厚度。
图 4 界面层上的热载子传输示意图
种接触, 界面层厚度 D具有与两个扩散极限之和

D1 + D2 相同的量级 ) ) ) 微米量级, D~ ( D1 + D2 )。
综合以上三种接触界面层厚度的界定, 在纳
微米厚度范围内的接触界面层内, 热载子 (声子、
电子、光子 )存在散射、扩散、反射、辐射等行为,
这些行为使热载子的平均自由程受到限制而变
关键词: 接触界面层; 热载子; 微尺度传热; 接触热传导
The invest iga tion of solid- solid contact in terfa ce th erm a l tr an sfer
Sh i Ling1, Yu X inm ing1, W angH uiling2, W u Xue jun1 ( 1. School of Chem istry and Environm ent Engineer ing, Jianghan Un iversity, Wuhan 430056, Ch ina; 2. Laboratory of Cryogen ics, H uazhong Un iversity of Sc ience and Technology, W uhan 430074, Ch ina) Abstr ac t: The concept of contact inte rface laye r was exp la ined. Based on the contact inte rface laye r, the th ickness and therma l conductivity of contact in terface laye r we re discussed, and the d iffusive and radiative therm a l conduction were occurred in contact inter face layer. The m echanism ofm icro- structure was shown up. The contact interface therm al resistance m ode l( C ITR ) was set up, the calcu lated va lue of the CITR was com pared with the va lue of DMM and exper im enta l datum, the results show that the lim ita tion of the DMM is hurd led. These are he lpful of the m icro- structure therm al transfer ana lysis. K eyword s: Contact interface layer, Therm al carr ie r, M icro- sca le the rm al transfe r, Contact conduction

直流输电技术9

Advantage of HTS DC Power TransmissionHuibin Zhao, Jianxun Jin, Xiao LuCenter of Applied Superconductivity and Electrical EngineeringUniversity of Electronic Science and Technology of ChinaChengdu, Chinajxjin@Abstract—High T c superconducting (HTS) cables and their application to build a DC power transmission system with the advantages of high transport current capability and no resistive transmission loss have been studied. Technical assessments of the DC electrical power transmission system behaviors with the use of the HTS DC cable technology have been carried out. The HTS DC cable and its DC power transmission system models have been built, and the analysis results obtained mainly include the magnetic field distribution of the HTS cable and the HTS DC power transmission system performances.Keywords-HTS cable; DC transmission system; power transmission loss; Ansoft / Maxwell; MatLab simulationI.I NTRODUCTIONThe resistive energy losses consumed on power transmission lines become enormous as the high capacity delivery power required by the dramatically developed society. Using high T c superconducting (HTS) cables HTS technology is an alternative way to resolve the principal technical difficulties to achieve high efficiency in power transmissions [1]. The HTS cable will especially benefit to DC power transmission due to zero resistive loss and lowering voltage levels [2,3]. The DC networks can operate with low voltage and high current allowing direct connection of the generators to the rectifiers, eliminating the need for high voltage insulation and transformers.The HTS DC cable technology will be presented in this paper. Power transmission performance studied by numerical simulations using the Matlab/Simulink, and analysis of the system loss and advantage will also be presented.II.D EVELOPMENT OF S UPERCONDUCTING C ABLESThere are a few countries which have initiated HTS cable development programs. The world’s first applicable HTS cable 30 m / 12.5 kV / 1.25 kA with three single phases [4] developed by the Southwire, was constructed during the first two quarters of 1999, installed by the third quarter of 1999, energized on Jan. 6, 2000, and inauguration on Feb. 18, 2000. The second superconducting 30 m / 30 kV / 104 MW cable system [5] designed with a room temperature dielectric and based on a HTS Bi-2223 tape technology has been developed, installed and operated in the public network of Copenhagen Energy in a two-year period between May 2001 and May 2003. The third HTS cable project for a 30 m / 35 kV / 2 kA, 3 phases, warm dielectric HTS power cable system [6] is operated in China, which has been installed in the China southern power grid at the Puji substation in Kunming, Yunnan province in 2004. Fig. 1 is the 30 m HTS cable operated at the Puji substation, the loads of the cable are the company’s production workshops. American, Japan et al plough into the investigation of HTS AC cables, their object and hope is to realize short distance (< 500 m), low loss, and high capacity power transmission. AC electric power transmission currently is the main way of power delivery and commonly used, which somehow results to HTS DC cable investigation lagged to HTS AC cables. The HTS zero resistance is observed only in DC currents, therefore a HTS DC cable and its DC transmission has better performance than for the AC case in which HTS AC loss exists. With the use of HTS DC cables, the transmission line voltages can be lower than conventional cables when the same power is transmitted because of the greater transmitting current capability, and also the AC/DC convertors on the termination of DC transmission cable become simple and lowcost consequently.Figure 1. HTS cable site at Puji substation in China [6].Compared with Bi-based HTS tapes - the first generation (1G) HTS wire and the current most suitable HTS wire for making cables [7,8], the Yttrium based oxide Y1Ba2Cu3O6+x tapes - the second generation (2G) HTS wires, its anisotropism is relatively infirmness and have higher I c near liquid nitrogen temperature with higher magnetic field tolerance. The I c of the 2G HTS tape produced has reached uniform high J c with applicable long lengths. According to the preparation process of the 2G HTS tapes, leaving out noble metal silver used to produce Bi-based HTS tapes, the cost is lower than the 1G Bi based HTS tapes, meanwhile the carrying capacity is higher than the 1G HTS tapes, and the superconducting performance is better at high magnetic field than the 1G HTS tapes. The 2G HTS tapes made in United States have reached to a kilometer level in a single length, and also a few hundred meters in a single length in Japan [9]. The HTS wire production cost hasProceedings of 2009 IEEE International Conference onApplied Superconductivity and Electromagnetic DevicesChengdu, China, September 25-27, 2009ID1191been reduced, but the practical HTS application cost still needs to add up the HTS material and its refrigeration cost [10]. The price predominance of new MgB 2 superconductor worked at 20-30 K is distinct. In recent years, some methods have been used to prepare MgB 2 tapes or long wires.Recently, a 0.5 m long experimental HTS DC cable has been built with the 2G HTS wires for technical verification, which has 1.6 kA transport current capability in total and its engineering current density J e ~ 104 A/cm 2 operated at 77 K.III. HTS DC C ABLE AND A NALYSISThe basic HTS DC cable configuration includes a protection shell, a thermal shield, an insulation layer, a HTS layer, and a cooling pipe. The designed HTS layer is made using the Bi-2223/Ag HTS wire. The J e in the level of 104 A/cm 2 - 77 K forms the HTS cable with a very high capability for highly rated transport currents, e.g. this gives 10 kA with cross-section area S = 2 cm 2 and filling factor λ (= S HTS /S HTSLayer ) = 0.5, and with surface field constant ~ 40 mT/kA.The rated HTS layer current is generally given by I = [1-k (J c )]J c S HTSLayer λ, where k (J c ) is a self field related coefficient.As is shown in Fig. 2, the cold dielectric (CD) HTS DC cable design has a concentric structure, the main body of this cable from inner to outer is former layer, compound conductor layer that is copper composite with paralleled placed HTS tapes, dielectric layer, compound shield layer, and thermally insulated double wall cryostat covering the whole cable. The liquid nitrogen goes through the hollow former and return at the other end in the space between the outer layers of HTS tapes and below the cryostat. The CD cable structure is shown in Table I. The total current is 1 kA in conductor layer, current density uses 50 A/mm 2, and the filling factor is one.Figure 2. HTS cable structure of DC power transmission.Magnetic fields in and around the experimental HTS cables are analyzed using Ansoft/Maxwell to simulate the field distribution, where the HTS is set as ordinary linear material with the total conductor layer current of 1 kA and relative permeability is 1.Figure 3. Field distribution along radius in a CD HTS cable model.Fig. 3 illustrates the simulated results of magnetic fields distribution along the cable radius from zero to 15 mm. The magnetic field is distributed mainly between the conductor layer and shield layer, almost zero field at the outer areas of the cable. The shield current with the same magnitude but reverse direction to the conductor current, and produced a shield to the magnetic fields produced by conductor current. The total fields act upon the HTS tape include the self field and field which generated by the other HTS tapes in the cable less than 0.025 T.The warm dielectric (WD) HTS DC cable design has also a concentric structure, the main components from inner to outeris former, compound conductor that is copper composite with paralleled placed HTS tapes, thermally insulated double wall cryostat, and ordinary dielectric material covering the whole cable. The liquid nitrogen goes through the hollow former and return at other channel. The WD cable structure is also shown in Table I. Fig. 4 illustrates the simulated results of magnetic fields distribution in and around the WD cable model in Ansoft/Maxwell, where (a) is magnetic fields distribution of the whole cable, and (b) is magnetic fields distribution alongthe radius from zero to 15 mm. There are magnetic fields distributed around the WD cable as shown in the Fig. 4, and it could introduce interference. The CD cable has a favorite field distribution than the WD cable.(a) Magnetic field distribution(b) Magnetic field distribution along the radius of the WD cableFigure 4. Distribution of magnetic field in WD HTS cable model.TABLE I.E XPERIMENTAL HTS C ABLE M ODELSComponent / Outer Radius (mm)CD cableWD cableLN 2 pipe / 8 LN 2 pipe / 8 Former / 9 Former / 9 Insulator1 / 9.4 Insulator1 / 9.4 Cu1 / 10.5 Cu1 / 10.5Conductor(YBCO Tape) / 10.8 Conductor(YBCO Tape) / 10.8 Cu2 / 11Cu2 / 11Insulator2 / 12 Heat insulator / 12 Cu3 / 13 - Shield(YBCO HTS Tape) / 13.3- Cu4 / 13.5 -0.0125B /T0.0250 5 10 15 R/mm B /T5 10 150.0125R/mm0.025IV. HTS DC T RANSMISSION S YSTEM AND A NALYSISThe HTS DC power transmission system mainly include some aspects as follows: HTS DC cable design; dc/ac conversion technology; joints between HTS wires and conventional metals; cooling technologies and so on. Fig. 5 shows the simplified HTS DC power transmission system model.AC systemAC systemCooling systemHTS DC LineTerminalTerminalFigure 5. HTS DC power transmission system schematic.Most of DC transmission systems adopt 12-pulse current convertors using two 6-pulse thyristor bridges connected in series. The converted current transformer provides current, reactive power required by the convertors is provided by a set of AC filters used to prevent the odd harmonic currents 11th, 13th and high pass filters from spreading out on the AC system on each side, and on the each side of the DC line has a smoothing reactor. Fig. 6 illustrates a DC power transmission system using a HTS cable. Matlab/Simulink has been used toset up a model to analysis the performance of a high-voltage direct current (HVDC) transmission system. The example in this section is modeling a HVDC transmission line using 12-pulse thyristor convertors. Perturbations can be applied to examine the system performance. A 1 kMW (500 kV, 2 kA) DC interconnection is used to transmit power from a 500 kV, 5 kMVA, 60 Hz system to a 345 kV, 10 kMVA, 50 Hz system.Figure 6. A thyristor-based 12-pulse HVDC link using a HTS cable.Fig. 7 shows the sending power and receiving power of theDC transmission system, the front segment of the curve corresponds to the ramped start-up, and the middle pulse segment of the curve corresponds to the DC line fault and AC grounding fault and the resuming process. The power obtained in simulation is from measuring the active power at the sendingAC and receiving AC system. The sending power subtracted by the receiving power gives the transmission system total power losses which include the loss consumed by transformers, filters, convertors and transmission lines.Figure 7. Sending and receiving power (p.u.).Fig. 8 shows that the loss of the system increases with the increase of resistance on transmission line and the decrease of transmission voltage level. When the line resistance keeps unchanged, reduces the voltage level, the loss of the system increases in the meantime. If HTS technologies are used, even if at a lower voltage level, the loss is still lower than that of the normal DC transmission system having a higher voltage level. Parameters are changed to deactivate the steps applied on the current references in the Master Control, and in the Inverter Control and Protection. In the DC Fault block, change the multiplication factor of 100 to 1, so that a fault is now applied at t = 0.7 s and ended at t = 0.8 s. The DC voltage and current on the side of rectifier and inverter under different line resistance shown in Fig. 9, where V 1 and I 1 are the voltage and current on the condition of 0.015 Ω/km DC line used and V 2 and I 2 are that of a 0.00015 Ω/km DC line adopted. the DC current increases to about 2.2 p.u. because of the discharge of capacitance on the DC line, the rectifier firing angle is forced to increase by the DC fault protection when detecting the low DC voltage on the side of rectifier, the rectifier now operates in inverter mode, The DC line voltage becomes negative and the energy stored in the line is returned to the AC system, causing rapid extinction of the fault current, about at 1.1 s, the DC line current come back to 1.0 p.u.. There are some oscillations produced on the voltage and current at the side of inverter during the fault used on the DC line at the side of rectifier. When reducing the line resistance, the DC current changes as the same regulation as the high line resistance, i.e. the DC fault restoration does not influenced when HTS DC cable used. Then in the DC Fault block, change the multiplication factor of 1 to 100, so that the DC fault is now eliminated. In the AC Fault block, change the multiplication factor in the switching times to 1, so that a line-to-ground fault is applied at t = 0.7 s at the inverter. Start the simulation and observe the waveforms shown in Fig. 10. A line-to-ground fault is applied and at the begin time of the ground fault applied, the DC line current on the side of rectifier and inverter up to 2 p.u., shown as I 1 andü Sending power--- Receiving powerthe voltage decrease to negative value shown as V1 quickly, during the AC grounding fault, the fault current drops to a small value, following with oscillations in the DC voltage and currents till the fault is ended at t = 0.8 s. The system recover approximately at t = 1.1 s. Then, decrease the line resistance to 0.00015 Ω/km, restart simulation and obtained V2 and I2, the change regulation of which are same to V1 and I1. We can conclude that the decrease of line resistance dose not influence the restoration of AC grounding fault too.Curve 1 is the loss of 400 kV, 2.5 kA, R = 0.015 Ω/km DC line.Curve 2 is the loss of 500 kV, 2 kA, R = 0.015 Ω/km DC line.Curve 3 is the loss of 400 kV, 2.5 kA, R = 0.00015 Ω/km DC line.Curve 4 is the loss of 500 kV, 2 kA, R = 0.00015 Ω/km DC line.Figure 8. Power transmission energy loss comparisons (p.u.).Figure 9.DC voltage and current at DC line fault.Figure 10. DC voltage and current at AC grounding fault.In this part, the thyristor-based HVDC link in MATLAB/Simulation is used to analyze the steady performance, which related to the line losses and voltage levels; and dynamic performance include the DC and AC fault and the restoration. The simulation results show that HTS technology can be applied to HVDC system with more benefits and no additional disadvantage.There are three components, i.e. convertor station, HTS cable system and grounding system, which are mainly included in the HTS DC transmission system. Therefore the total loss includes the convertor station loss on each side of the cable system, the loss of the cable system itself and grounding system.The loss of convertor station can be obtained by calculating the loss of each component in the convertor station, the percentages of different loss items of convertor station [10]: Convertor transformers ~50 %; Thyristor valves ~35 %; Smoothing reactors ~5 %; AC filters ~5 %; Other losses ~5 %. It shows that convertor transformers and thyristor take up the principal loss of the convertor station. So reducing the loss consumed by convertor transformers and thyristors is critical to decrease the total convertor station loss.HTS DC cable has no reactive power and virtually no loss in the insulation, leaving only the heat leak as a loss source. This makes the design and optimization of DC HTS cables much less complex than in the AC case.R EFERENCES[1]J. X. Jin, “High efficient dc power transmission using high-temperaturesuperconductors,” Physica C, vol. 460–462, pp. 1443–1444, 2007.[2]Q. Huang, J. X. Jin, and J. B. Zhang, “Simulation analysis of longdistance dc transmission based on HTS technology,” Electric Power, vol. 39, no. 3, pp. 45-49, March 2006.[3]J. X. Jin, C. M. Zhang, and Q. Huang, “DC power transmission analysiswith high T c superconducting cable technology,” Nature Sciences, vol.1, no. 1, pp. 27–32, Dec., 2006.[4]J. P. Stovall, J. A. Demko, P. W. Fisher, M. J. Gouge, J. W. Lue, U. K.Sinha, J. W. Armstrong, R. L. Hughey, D. Lindsay, and J. C. Tolbert, “Installation and operation of the southwire 30-meter high-temperature superconducting power cable,” IEEE Trans. on Applied Superconductivity, vol. 11, no. 1, pp. 2467-2472, March 2001.[5]O. Tønnesen, M. Daumling, K. H. Jensen, S. Kvorning, S. K Olsen, C.Træholt, E. Veje, D. Will´en, and J. Østergaard, “Operation experienceswith a 30 kV/100 MVA high temperature superconducting cable system,” Superconductor Sci. Tech., vol. 17, pp. S101–S105, 2004.[6]Y. Xin, B. Hou, Y. F. Bi, K. N. Cao, Y. Zhang, S. T. Wu, H. K. Ding, G.L. Wang, Q. Liu, and Z. H. Han, “China’s 30 m, 35 kV/2 kA ac HTSpower cable project,” Supercond. Sci. Technol., vol. 17, pp. S332–S335,2004.[7]J. X. Jin, C. Grantham, H. K. Liu, and S. X. Dou,“(Bi,Pb)2Sr2Ca2Cu3O10+x Ag-clad high-T c superconducting coil and its magnetic field properties,” Philosophical Magazine B, vol. 75, no. 6, pp.813-826, 1997.[8]J. X. Jin and S. X. Dou, “A high temperature superconducting winding andits techniques,” Physica C, vol. 341-348, no. 1-4, pp. 2593-2594, 2000. [9]Y. W. Ma, Science and News, March 2007, Institute of Sci. and Tech.Information of China.[10] D. Politano, M. Sjostrom, G. Chnyder, and J. Rhyner, “Technical andeconomical assessment of HTS cables,” IEEE Transactions on Applied Superconductivity, vol. 11, no. 1, pp. 2477-2480, March 2001.。

烧结法制备YBa2Cu3O7-δ系列超导体的研究概况

烧结法制备ＹＢａ２Ｃｕ３Ｏ７－δ系列超导体的研究概况摘要YBa2Cu3O7-δ系列超导体是高温超导材料中研究最多和应用最为广泛的超导体之一。

本文概括介绍了国内外有关烧结法制备YBa2Cu3O7-δ系列超导体的弱连接问题、输运性质、电磁性质及烧结工艺等方面的研究概况，对高临界电流密度YBa2Cu3O7-δ超导体的制备及理论分析具有重要的参考价值。

关键词YBa2Cu3O7-δ超导体，烧结法，晶粒间界1引言烧结法是传统制备YBa2Cu3O7-δ超导体的传统方法，由于所制取样品的临界电流密度很低，因此没有多大的实用价值，然而作为其它工艺的初级阶段或研究基础[1]，仍具有很大的研究价值。

以下是国内外有关烧结法制备YBa2Cu3O7-δ系列超导体的弱连接问题、输运性质、电磁性质及烧结工艺等方面的研究概况。

2与超导体晶粒间界的弱连接相关的概念概括各种研究结果[2～5]可知，晶界弱连接产生的原因主要有以下几点：（1）超导晶粒取向的各向异性导致大角度晶界处的弱连接。

弱连接引起了超导电流的重新分布，同时穿过大角度晶界电流的流量也会受到严重限制[6]，因此超导体的临界电流密度大大降低。

（2）晶界处化学成分（如阳离子或氧的化学配比）的偏差、第二相的存在以及不佳的晶体结构等都会导致晶界处的弱连接。

晶界处的第二相粒子一般都是非超导相粒子。

（3）超导体热膨胀的各向异性导致了晶界处的微裂纹﹑位错及孔隙等缺陷的存在，晶界处的缺陷严重影响着电子结构，因此降低了超导体的临界电流密度。

大量文章表明[7～9]，晶界区的临界电流密度与温度满足以下关系:JC～(1-T/TC)n。

n值不同,表明晶界弱连接的类型不同。

n=1、1.5、2时,结的类型分别为SIS(Superconductor Insulator Superconductor)、SINS(Superconductor Insulator Metal Superconductor)和SNS(Superconductor Metal Superconductor)。

作文未来超导技术450字的

作文未来超导技术450字的英文回答：Superconducting technology is poised to revolutionize our future in numerous ways. With its ability to conduct electricity without any resistance, superconductors have the potential to greatly enhance the efficiency and performance of various devices and systems. From transportation to healthcare, superconducting technology holds immense promise.In the field of transportation, superconducting technology can lead to the development of high-speed trains that can travel at unprecedented speeds. Maglev trains, which use superconducting magnets to levitate and propel the train, can reach speeds of up to 600 km/h. This not only reduces travel time significantly, but also offers a more comfortable and efficient mode of transportation.Moreover, superconducting technology can revolutionizethe healthcare industry. Magnetic resonance imaging (MRI) machines, which utilize superconducting magnets, provide detailed and accurate images of the body's internal structures. This technology has greatly advanced medical diagnostics and has become an indispensable tool for doctors in diagnosing various conditions and diseases.Furthermore, superconducting technology has the potential to greatly enhance the efficiency of power transmission and storage. Superconducting cables can transmit electricity with minimal losses, reducing energy wastage and increasing the overall efficiency of the power grid. Additionally, superconducting energy storage systems can store excess energy during off-peak hours and release it during peak demand, ensuring a stable and reliable power supply.中文回答：超导技术有望在许多方面彻底改变我们的未来。

功能材料相关文献翻译(中文+英文)

功能材料相关文献翻译（中文+英文）功能材料功能材料是新材料领域的核心，是国民经济、社会发展及国防建设的基础和先导。

它涉及信息技术、生物工程技术、能源技术、纳米技术、环保技术、空间技术、计算机技术、海洋工程技术等现代高新技术及其产业。

功能材料不仅对高新技术的发展起着重要的推动和支撑作用，还对我国相关传统产业的改造和升级，实现跨越式发展起着重要的促进作用。

功能材料种类繁多，用途广泛，正在形成一个规模宏大的高技术产业群，有着十分广阔的市场前景和极为重要的战略意义。

世界各国均十分重视功能材料的研发与应用，它已成为世界各国新材料研究发展的热点和重点，也是世界各国高技术发展中战略竞争的热点。

在全球新材料研究领域中，功能材料约占 85 % 。

我国高技术(863)计划、国家重大基础研究[973]计划、国家自然科学基金项目中均安排了许多功能材料技术项目(约占新材料领域70%比例)，并取得了大量研究成果。

当前国际功能材料及其应用技术正面临新的突破，诸如超导材料、微电子材料、光子材料、信息材料、能源转换及储能材料、生态环境材料、生物医用材料及材料的分子、原子设计等正处于日新月异的发展之中，发展功能材料技术正在成为一些发达国家强化其经济及军事优势的重要手段。

超导材料以NbTi、Nb3Sn为代表的实用超导材料已实现了商品化，在核磁共振人体成像(NMRI)、超导磁体及大型加速器磁体等多个领域获得了应用;SQUID作为超导体弱电应用的典范已在微弱电磁信号测量方面起到了重要作用，其灵敏度是其它任何非超导的装置无法达到的。

但是，由于常规低温超导体的临界温度太低，必须在昂贵复杂的液氦(4.2K)系统中使用，因而严重地限制了低温超导应用的发展。

高温氧化物超导体的出现，突破了温度壁垒，把超导应用温度从液氦( 4.2K)提高到液氮(77K)温区。

同液氦相比，液氮是一种非常经济的冷媒，并且具有较高的热容量，给工程应用带来了极大的方便。

另外，高温超导体都具有相当高的上临界场[H c2 (4K)>50T]，能够用来产生20T以上的强磁场，这正好克服了常规低温超导材料的不足之处。

A High-Temperature Superconducting Maglev Dynamic Measurement System

A High-Temperature Superconducting MaglevDynamic Measurement SystemJiasu Wang,Suyu Wang,Changyan Deng,Youwen Zeng,Longcai Zhang,Zigang Deng,Jun Zheng,Lu Liu, Yiyun Lu,Minxian Liu,Yaohui Lu,Yonggang Huang,and Ya ZhangAbstract—The dynamic measurement of high temperature superconducting(HTS)magnetic levitation(Maglev)vehicle is a very important and difﬁcult problem.In order to investigate the dynamic characteristics behavior of HTS Maglev,an HTS Ma-glev dynamic measurement system(SCML-03)was successfully developed in Applied Superconductivity Laboratory(ASCLab)of Southwest Jiaotong University,P.R.China.The system is mainly constituted by the circular permanent magnet guideway(PMG), liquid nitrogen vessel,data acquisition and processing,mechanical drive,autocontrol and so on.The PMG isﬁxed along the circum-ferential direction of a big circular disk with diameter1500mm. The maximum linear velocity of the PMG is about300km/h when the circular disk rotates round the central axis at1280rpm.The liquid nitrogen vessel with high temperature superconductors is placed above the PMG,and the vessel is not three-dimensional rigid connection with measurement sensor devices.These sensors can detect weak force change from three-dimensional directions. The maximal vertical and horizontal support force of the system are3350N and500N,respectively.Test process and results of the HTS Maglev dynamic test system are reported.Index Terms—Dynamics,high-temperature superconductors, Maglev,YBCO bulk.I.I NTRODUCTIONI N ORDER to investigate the magnetic levitation(Maglev)properties of high temperature superconducting(HTS) Maglev vehicle over the NdFeB permanent magnet guideway (PMG),an HTS Maglev measurement system(SCML-01)was developed in1999[1].The SCML-01can measure Maglev properties between an YBaCuO bulk and a permanent magnet (PM)or PMG,which was principally employed in onboard HTS Maglev equipment over one or two PMGs.Based on the original research results from SCML-01,theﬁrst man-loading HTS Maglev test vehicle in the world was successfully devel-oped in2000[2].Soon,several HTS Maglev vehicles prototype over the NdFeB PMG got birth in Germany,Russia,Brazil and Japan[3]–[5].Afterﬁve years,an update HTS Maglev Measurement System(SCML-02)with more functions and higher precision was developed to extensively investigate the Maglev properties of YBaCuO bulk with PM or PMG[6].A lot of precious experimental results were obtained[7],like levitation force,guidance force and their stiffness,and cross stiffness.All these experimental parameters are very helpfulManuscript received August22,2007.This work was supported by the Na-tional High Technology Research and Development Program of China(National 863Program)(2005AA306150)and the National Natural Science Foundation in China(50377036,50677057).The authors are with the Applied Superconductivity Laboratory(AS-CLab),Southwest Jiaotong University,Chengdu610031,China(e-mail: jsywang@;asclab@).Digital Object Identiﬁer10.1109/TASC.2008.920568Fig.1.The design scheme of principal part of the HTS Maglev dynamic testsystem(not including power supply and measurement control desk).to evaluate load ability of the HTS Maglev vehicle.But therunning performance above PMG can not be measured by theabove measurement systems.For the further engineering application of the HTS Maglevvehicle,the dynamic Maglev properties should be clearly un-derstood.From this viewpoint,an HTS Maglev dynamic testsystem(SCML-03)has been designed and successfully devel-oped in Applied Superconductivity Laboratory(ASCLab)ofSouthwest Jiaotong University,P.R.China.The test process andresults of the HTS Maglev dynamic test system are reported inthis paper.II.S YSTEM D ESCRIPTIONWhen the HTS Maglev vehicle runs along the PMG,it isdifﬁcult to measure its dynamic properties.In SCML-03,therotational motion of a circular PMG instead of the motion ofYBaCuO bulk was taken to equivalently measure the dynamicinteraction,that is,the circular PMG can rotate to different speedwhile the onboard HTS Maglev equipment isﬁxed above thePMG,as shown in Fig.1.The main part of SCML-03,shown in Fig.1,is composedof the vertical and horizontal servo motors,three-dimensionalmeasurement,liquid nitrogen vessel,circular PMG,drive de-vice,data acquisition and processing,autocontrol and so on.The principal part of the SCML-03is shown in Fig.2.Thetotal technical parameters of the principal part of the SCML-03are3.3m long,2.4m wide and3.15m high.The total weight is13.95t(circular disk of PMG weight of0.6t included).1051-8223/$25.00©2008IEEEFig.2.The photo of principal part of the HTS Maglev dynamic test system(No the measurement control desk).A DC motor is used to drive the circular PMG to rotate and control the rotational speed.The rotation direction of the DC motor is translated into the horizontal rotation direction of the circular PMG by a gear redirection case.The circular PMG is ﬁxed along the circumferential direction of a big circular disk with diameter1500mm.The rotating unbalance of the big cir-cular disk is less than20g.The maximum linear velocity of the PMG is about300km/h when the circular disk rotates round the central axis at1280rpm.The rotation speed error of the circular disk is less than3%.The dynamic vertical levitation force is measured when the circular PMG is rotated by different speed.The three-dimensional measuring seat isﬁxed on the hori-zontal load.The seat can be moved along the horizontal direc-tion which is perpendicular to the tangent direction of the cir-cular PMG.Therefore,the HTS Maglev dynamic guidance force can be measured at one time.Six force sensors are used to mea-sure the vertical,transverse,and longitudinal direction forces on the liquid nitrogen vessel.In order to measure the three-dimen-sional dynamic response the liquid nitrogen vessel is connected to the three-dimensional measuring seat by the elastomers. The autocontrol of all components are completed by the total control desk.Both measurement and control soft is developed on basis of Labview soft of National Instrument.The servo motor movement and the circular PMG speed are controlled by both program soft and relative control card.The data acquisition and processing are achieved by self-developed program.In order to calibrate measurement precision of the dynamic measurement system,11ch Noise&Vibration Measurement System made in B&K are used.III.T HE F UNCTIONS AND T ECHNICAL S PECIFICATIONS The SCML-03can measure the dynamic properties in oppo-site motion between the vehicle and the PMG.The main mea-surement functions include:1)Dynamic stability measurement of HTS Maglev equipment(liquid nitrogen vessel included HTSCs)at different ve-locity;2)Measurement of levitation force and guidance force of bothsingle and multi HTSCs specimens;3)Measurement of levitation force stiffness and guidanceforce stiffness of both single and multi HTSCsspecimens;Fig.3.The measurement scene of the HTS Maglev dynamic test system. 4)Measurement of levitation force and guidance force changeat different levitation gap;Main technical speciﬁcations:1)Diameter of the circular PMG1500mm;2)Maximal linear speed of the circular PMG300km/h;3)Rotation speed precision of the circularPMG3%;4)Vertical maximal displacement200mm;5)Horizontal maximaldisplacement50mm;6)Positionprecision0.05mm;7)Vertical maximal support force3350N;8)Horizontal maximal support force500N;9)Force sensorprecision1%.IV.S TABILITY OF THE D YNAMIC T EST S YSTEMThe important properties of the dynamic test system are the self stability.The rotating unbalance of the PMG circular disk is less than20gm.The rotating unbalance value can satisﬁed the system measurement needs.The other important parameter of the dynamic test system is the self stability of the liquid ni-trogen vessel and the body frame.In order to conﬁrm the self sta-bility,11ch Noise&Vibration Measurement System are used. A4507-004B accelerometer isﬁxed on the body frame,and four4507-004B accelerometers areﬁxed on the clamp device of liquid nitrogen vessel.The vibrations of the perpendicular and horizontal directions on the clamp device are measured by two sensors respectively.The photo of the measurement scene of the SCML-03is shown in Fig.3.The vibration spectrums of the body frame and the clamp device of the liquid nitrogen vessel are measured at the rota-tion speed of50rpm,100rpm,200rpm,300rpm,and400 rpm,respectively.The vibration spectrum of the clamp device of the liquid nitrogen vessel includes both the perpendicular di-rection and the horizontal direction.The auto-spectrum of the body frame at400rpm is shown in Fig.4.The cross-spectrums of the perpendicular direction and the horizontal direction on the liquid nitrogen vessel at400rpm are shown in Figs.5and6, respectively.There is not the liquid nitrogen vessel on the clamp device when these vibration spectrums are measured.Fig.7shows the vibration measuring results of the body frame and the clamp device of the liquid nitrogen vessel(the perpendicular and the horizontal direction)at the rotation speed of50rpm,100rpm,200rpm,300rpm,and400rpm, respectively.The Fig.7(a)shows the measuring vibration results without the liquid nitrogen vessel on the clamp device. The Fig.7(b)shows one with the liquid nitrogen vessel.AfterWANG et al.:A HIGH-TEMPERATURE SUPERCONDUCTING MAGLEV DYNAMIC MEASUREMENT SYSTEM793Fig.4.The auto-spectrum of the body frame at 400rpm.Fig.5.The cross-spectrum of the perpendicular direction on the clamp device of the liquid nitrogen vessel at 400rpm.Fig.6.The cross-spectrum of the horizontal direction on the clamp device of the liquid nitrogen vessel at 400rpm.twenty-four YBCObulks in the vessel is cooled the zero ﬁeld,vibration properties are measured at the levitation gap of 20mm and the lateral displacement of 0mm.Experimental results show the vibration of the body frame is increased quickly with increase of the rotation speed,and the vibration of the clamp device with or without the liquid nitrogen vessel is increased slowly with increase of the rotation speed.It indicates that the three-dimensional measuring seat have the function of vibration isolation.The vibration of the clamp device with the liquid nitrogen vessel can satisﬁed measurementrequirements.Fig.7.The vibration measuring results of the body frame and the clamp device of the liquid nitrogen vessel (the perpendicular and the horizontal direction)at the rotation speed of 50rpm,100rpm,150rpm,200rpm,300rpm,and 400rpm,respectively:(a)the measuring results without the liquid nitrogen vessel on the clamp device and (b)one with the liquid nitrogenvessel.Fig.8.Measurement results of the levitation forces of YBCO bulk by zero ﬁeldcooling.Fig.9.Measurement results of the guidance forces of YBCO bulk at 15mm levitation gap of the ﬁeld cooling.V .M EASUREMENT OF HTS M AGLEV P ROPERTIESThe main distinguish between the SCML-03and previous HTS Maglev measurement system [1]–[6]is to measure the Ma-glev performance at the running case.By SCML-03,both levi-tation forces and guidance forces are measured experimentally at different velocity.The experimental results of the levitation forces and the guid-ance forces of YBCO bulk measured with the SCML-03are shown in Fig.8and Fig.9respectively.The levitation forces of YBCO bulks are measured by zero ﬁeld cooling (ZFC),and the guidance forces of YBCO bulk are measured at 15mm ﬁeld cooling height.Those measurement results veriﬁed that the794IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY ,VOL.18,NO.2,JUNE2008Fig.10.(a)Experimental results of the levitation force of zero ﬁeld cooling YBCO bulks at time intervals of 12s and (b)special rotation speed (the levitation gap of 10mm).Fig.11.Experiment results of the guidance force of ﬁeld cooling YBCO bulks at the time intervals of 12s,the levitation gap of 15mm,and special rotation speed.SCML-03is applicable for measurement of the levitation and the guidance forces at movement state.In order to proof the applicability of the measurement re-sults of the levitation forces and the guidance forces of YBCO bulks,the changes of the measurement results with different measuring time and different rotation speed are investigated ex-perimentally.The experiment conditions are the rotation speed of 50rpm,100rpm,200rpm,300rpm,and 400rpm,respec-tively,and each time intervals of 12s.The experimental results of the levitation force of ZFC YBCO bulks at the time intervals of 12s and special rotation speed are shown in Fig.10.The ex-perimental results are measured at the levitation gap of 10mm.Fig.10indicates that the changes of measured levitation forces at time intervals of 12s are small,especially at 300rpm and 400rpm.The higher PMG rotation speed,the smaller of levitation forces change.At the levitation gap of 10mm the most changes of measured levitation forces in 48s period are 0.54N (300rpm)and 0.10N (400rpm),respectively.The levitation forces decrease with the increase of rotation speed.The decrease value of the levitation forces is 22.98N when the rotation speed is changed from 50rpm to 400rpm at the time intervals of 12s,and the decrease percent of the lev-itation forces is 7.4%.The reason of decrease of the levitation forces is probably attributed to the little uniformity of the cir-cular PMG’s magnet ﬁeld along the circumferential direction.The experimental results of the guidance force of ﬁeld cooling YBCO superconductor bulks at the time intervals of 12s,levitation gap of 15mm,and special rotation speed are shown in Fig.11.It indicates that the changes of measuredguidance forces at the time intervals of 12s are small,especially at 300rpm and 400rpm.The higher PMG rotation speed,the smaller of levitation forces change.The experimental results of the guidance forces are not better than that of the levitation forces.The most changes of measured guidance forces in per 48s are 0.28N (300rpm)and 0.79N (400rpm),respectively.VI.C ONCLUSIONIn order to investigate the dynamic force behavior of HTS Maglev,an SCML-03HTS Maglev dynamic test system was successfully developed in Applied Superconductivity Labora-tory (ASCLab)of Southwest Jiaotong University,P.R.China.To our knowledge,SCML-03is the ﬁrst dynamic test system which can measure the dynamic levitation and guidance force properties to simulate HTS Maglev vehicle runs above PMG within 300km/h forward velocity up to now.The main measurement functions include the dynamic stability of HTS Maglev equipment (liquid nitrogen vessel included HTSCs),the levitation force and guidance force of both single and multi HTSCs specimens,the levitation force and guidance force rigidity of both single and multi HTSCs specimens,the levitation force and guidance force change at levitation gap,and so on.The main technical speciﬁcations include the diameter of the circular PMG 1500mm,the rotating unbalance of the big cir-cular disk less than 20gm,the maximal linear speed of the cir-cular PMG 300km/h,the rotation speed precision of the circularPMG 3%,the vertical maximal displacement 200mm,the ver-tical maximal support force 3350N,and the horizontal maximal support force 500N.The vibration of the clamp device with the liquid nitrogen vessel is increased very slowly with the increase of rotation speed,so the vibration of the clamp device can satisﬁed mea-surement requirements.Moreover Maglev parameters at the dif-ferent rotation speed are obtained by the feasible measurement system,SCML-03.A CKNOWLEDGMENTThe authors thank Mr.R.Zhao for his help in skilled fabrication.R EFERENCES[1]J.S.Wang et al.,“High Tc superconducting magnetic levitation mea-surement system,”(in Chinese)High Technol.Lett.,vol.10,no.8,pp.56–58,2000.[2]J.S.Wang et al.,“The ﬁrst man-loading high temperature supercon-ducting Maglev test vehicle in the world,”Physica C ,vol.378–381,pp.809–814,2002.[3]L.Schultz et al.,“Superconductively levitated transport system—TheSupraTrans project,”IEEE Trans.Appl.Supercond.,vol.15,pp.2031–2035,2005.[4]R.M.Stephan,R.Nicolsky,M.A.Neves,A.C.Ferreira,and R.deAndrade,Jr.et al.,“A superconducting levitation vehicle prototype,”Physica C ,vol.408–441,pp.932–934,2004.[5]M.Okano,T.Iwamoto,M.Furuse,S.Fuchino,and I.Ishii,“Run-ning performance of a pinning-type superconducting magnetic levita-tion guide,”J.Phys.:Conf.Ser.,vol.43,pp.999–1002,2006.[6]S.Y.Wang et al.,“An update high-temperature superconducting Ma-glev measurement system,”IEEE Trans.Appl.Supercond.,vol.17,no.2,pp.2067–2070,2007.[7]J.S.Wang and S.Y.Wang,“Synthesis of bulk superconductors andtheir properties on permanent Magnet guideway,”in Frontiers in Su-perconducting Materials ,A.Narlikar,Ed.Berlin,Germany:Springer Verlag,2005,pp.885–912.。

SUPERCONDUCTING ELEMENT

专利名称：SUPERCONDUCTING ELEMENT 发明人：IWASHITA SETSUYA,NATORI EIJI 申请号：JP18210690申请日：19900710公开号：JPH0469985A公开日：19920305专利内容由知识产权出版社提供摘要：PURPOSE:To improve yield and to obtain an oxide superconducting element having high reproducibility and high integration by miniaturizing the element to be continuously miniaturized at the same position by ion implanting in an ultrahigh vacuum state therefor. CONSTITUTION:A superconducting thin film 16 is formed in an MBE chamber, and three elements are simultaneously deposited by K-cell by using metals of yttrium 10, barium 11 and copper 12 as substances to be deposited. Then, the film is transferred into an ion implanting device evacuated in vacuum to pressure of the same degree as that in the chamber by opening a valve 7. It is previously evacuated in vacuum to shorten the time as compared with the case in which film forming and miniaturizing are independently conducted. It is ion implanted to form an insulating part 17. Thereafter, Ag 18 is formed, two superconducting electrodes are connected to form a microbridge, a metal mask 20 is injected directly under a substrate, and Ag 9 is deposited about800Angstrom by using a K-cell.申请人：SEIKO EPSON CORP更多信息请下载全文后查看。

作文未来超导技术450字的

作文未来超导技术450字的英文回答：Superconducting technology has the potential to revolutionize the future in numerous ways. One of the most exciting prospects is the development of high-speed magnetic levitation trains. These trains use superconducting magnets to float above the tracks, eliminating friction and allowing for incredibly fast and efficient travel. For example, the maglev train in Shanghai can reach speeds of up to 430 km/h, making it one of the fastest trains in the world.Another area where superconducting technology is making a big impact is in medical imaging. MRI machines use superconducting magnets to produce detailed images of the inside of the body. These machines are incredibly valuable for diagnosing and treating a wide range of conditions, from tumors to torn ligaments. In fact, I recently had an MRI scan on my knee after a skiing accident, and the imageswere so clear that the doctors were able to pinpoint the exact location of the injury.In the future, I believe that superconductingtechnology will continue to advance and become even more integrated into our daily lives. For example, we may seethe development of superconducting power lines that can transmit electricity with minimal loss, leading to more efficient and sustainable energy distribution. Additionally, superconducting quantum computers have the potential to revolutionize computing by solving complex problems at speeds that are currently unimaginable.Overall, the future of superconducting technology is incredibly exciting, and I can't wait to see how it will continue to shape the world around us.中文回答：超导技术有着许多潜力，未来有望在多个领域引起革命性变化。

超导合金英文作文

超导合金英文作文Superconducting alloys are a fascinating area of research in the field of materials science. These alloys possess unique properties that make them highly desirablefor various applications. For instance, they exhibit zero electrical resistance at low temperatures, allowing for efficient transmission of electricity. This remarkable characteristic has the potential to revolutionize power generation and distribution systems.Moreover, superconducting alloys also have the abilityto generate intense magnetic fields. This property opens up possibilities for their use in magnetic resonance imaging (MRI) machines, particle accelerators, and even levitating trains. Imagine a world where trains float above the tracks, eliminating friction and enabling high-speed transportation!In addition to their electrical and magnetic properties, superconducting alloys are also known for their incredible strength. This strength, combined with their ability towithstand extreme temperatures, makes them ideal for applications in aerospace and defense industries. These alloys can be used to build lightweight yet sturdystructures for aircraft and spacecraft, enhancing their performance and durability.Furthermore, superconducting alloys have shown promisein the field of energy storage. By utilizing their abilityto store large amounts of electrical energy, these alloys can be used to develop more efficient and compact batteries. This could revolutionize the way we store and utilize energy, leading to a more sustainable and environmentally friendly future.Additionally, superconducting alloys have the potential to revolutionize the field of quantum computing. Their unique properties allow for the creation of qubits, the basic building blocks of quantum computers. These qubitscan store and process information in a way that is exponentially faster than traditional computers. This could lead to breakthroughs in fields such as cryptography, drug discovery, and optimization problems.In conclusion, superconducting alloys are a fascinating area of research with immense potential. Their unique properties make them highly desirable for various applications, ranging from power generation and transportation to aerospace and quantum computing. Continued research and development in this field will undoubtedly lead to exciting advancements that will shape the future of technology.。

超导状态下的量子锁定

题目：超导状态下的量子锁定刘心岩摘要：超导现象从发现至今已有100多年的历程。

从超导现象与量子力学结合在一起之后，人们不在仅仅注重现象，而是研究超导现象的本质和原因。

BCS理论，迈纳斯效应，量子力学使人们超导现象有了质的飞跃。

不断刷新着临界温度。

并因此发现许多新的现象。

关键词：超导现象量子力学抗磁性新兴技术正文：1 911年荷兰物理学家卡姆林·奥尼斯发现水银温度在4K附近其电阻完全消失，几十年间科学家不断发现多种元素或合金在特定的温度下电阻突变为0的现象，称为超导现象。

然而。

超导现象包含两个方面，通常我们熟知的是零电阻，然而电磁现象的相互联系暗示我们，超导体一定有着特殊的磁效应。

将一小块超导体冷却至临界温度，置于磁铁之上，发现超导体悬浮在磁铁之上，并且随着磁铁的移动甚至翻转而移动，就像是被锁定在磁铁上一样，我们把这种现象称为量子悬浮或者量子锁定。

即所谓的迈斯纳效应。

每一个物理现象都让我们不禁追问背后的原因。

这是怎样特殊的磁效应。

量子力学作出回答，超导体在临界温度下表现出完全的抗磁性。

超导体一旦进入超导状态，体内的磁通量将全部被排出体外，磁感应强度恒为零，且不论对导体是先降温后加磁场，还是先加磁场后降温，只要进入超导状态，超导体就把全部磁通量排出体外。

外加磁场无法进入或（严格说是）大范围地存在于超导体内部，这是超导体的另一个基本特性。

通过自发的环形电流排斥穿过导体内部的磁感线。

当把超导体放进磁场中时，由于电感应作用，在超导体表面形成感应电流I（永久电流），在超导体内部，感应电流I激发的磁场和外磁场等值反向，相互抵消。

后来人们还做过这样一个实验，在一个浅平的锡盘中，放入一个体积很小磁性很强的永久磁铁，然后把温度降低，使锡出现超导性。

这时可以看到，小磁铁竟然离开锡盘表面，飘然升起，与锡盘保持一定距离后，便悬空不动了。

这是由于超导体的完全抗磁性，使小磁铁的磁力线无法穿透超导体，磁场发生畸变，便产生了一个向上的浮力。

超导及超导材料的应用

Superconductivity and Application【Abstract】Superconductivity refers to the phenomenon that materials’ resistance drop to zero in a certain temperature. A material with such characteristic is called a superconducting material. Since the superconducting material was discovered in 1911,scientists have got rapid progress on it. The critical temperature of superconductor has increased from several kelvin to dozens kelvin. The application of superconducting technology has great potential and development prospects. This article introduced the development of superconductivity,the properities of superconductivity and the application of superconductivity. It is believed that with the development of superconductivity, superconductor will be used in more high-tech fields.【Key words】superconductivity；superconductor；application1.Development of superconductivity1.1 History of SuperconductivityIn 1911, the Dutch physicist Onnes[1] cooled mercury to -40℃, solidify the mercury into a linear. Then he lowered the temperature 4.2K (-269 ° C) using liquid nitrogen. And added voltage across the mercury .He found that the resistance disappeared when the temperature was slightly below 4.2K. He called this new state of mercury as superconducting state. Later, he also found that Tin and Lead also have superconductivity.The temperature superconductivity occurs near absolute temperature(-273℃). The practical value is not high. In order to find superconducting phenomenon of materials with a high critical transition temperature, countless scientists struggled for nearly 60 years. Until 1973, some British and American scientists had found a niobium - germanium alloy ,whose critical temperature is 23K (-250 ℃). Later,a study led by the Chinese-American scholar Zhu Jingwu and Chinese physicist Zhao Zhongxian found superconducting materials with critical temperature of 98K (-175 ℃) and 78.5K (-194.5 ℃). In 1991, scientists from the United States and Japan found a spherical carbon (carbon 60) molecules has superconductivity ,if incorporate of potassium, cesium, neodymium and other elements. Some scientists also predicted that materials may become superconducting in room temperature, and then superconducting materials may cause an industrial and technological revolution in the world, like semiconductor materials.1.2 Development of superconductivityThe development of superconducting technology can be divided into three stages: the study of low temperature superconductivity theory, the influence of superconducting material on magnetic field and the research of high temperature superconducting material.1.2.1 The development of low temperature superconducting materials.In 1933, Meissner and Olsenfeld[2] discovered another important property. When the metal in the superconducting state, the original magnetic field present in the body was squeezed out . So the superconducting magnetic flux density is zero. People definited this phenomenon as the Meissner effect. The discovery of the Meissner effect realized people that the superconducting state is actually a thermodynamic state. The complete conductivity and the complete diamagnetism are the two basic characteristics of superconductor. In 1955, Bartin proposed three key factors for superconducting phenomena: electron phonon interaction; energy gap exists; Velocity (momentum space).In 1955, Cooper uses the quantum field theory,to consider the role of mutual attraction from the dynamic.They found that two electronic ,whose momentum and spin are the same size but in the opposite direction ,combined with each other near the Fermi surface.This combination of electron pairs was named "Cooper pair".The two electrons of Cooper pairs are in a bound state , the energy is even lower than the Fermi surface energy, forming a superconducting energy gap.Until 1957,the first article on superconductivity was published in the Journal Physical Review.And the theory was named BCS theory. The establishment of BCS theory indicates that the explanation of superconductivity has entered the microcosmic stage from the macroscopic phenomenological stage.1.2.2 The development of high temperature superconducting materials.In1986,Muller and Bai Nuode found La-Ba-Cu-O superconductor has a transition temperature of 36K,in Swiss IBM laboratory.Which opened the development of high-temperature superconductivity.In the end of 1987,the critical superconducting temperature of the T1-Ba-Ca-Cu-O material was increased to 125K.Which means the development and application of superconductor has entered a new level.In April 2001,Tsinghua University Research Center of Applied Superconductivity successfully developed a 340m high-temperature superconducting Bismuth line[3].And at the end of that year ,the first high-temperature Bismuth wire production line was completed.In October 10, 2009, the United States scientists synthetic material (Tl4Ba) Ba2Ca2Cu7O13 +, it’s superconducting temperature was 254K, only 19 ℃to the freezing point . It is a greatsignificance for the promotion of practical application of superconductivity.In short,the development of superconducting materials has gone through a period,from simple to complex, from single system to multi-system process. The discovery of copper high-temperature superconductors has a huge impact on the field of science and technology.2.The properities of superconducting materials2.1 Zero resistance effectWhen temperature drops below a certain value,the resistance of the superconducting material suddenly becomes zero.This is called the zero resistance effect[4] of the superconducting material, which is also known as superconductivity.In 1911, Kamerlin Onnes found an unusual phenomenon: as the temperature dropped, the resistance of mercury did not descend smoothly, but suddenly dropped to zero at 4.15K. This is the first time people discovered the superconductivity. In later experiments ,people found that the mutation temperature has nothing to do with mercury’s purity,only concluded that the more pure mercury is, the more sharp mutations shows.Scientists also found this properity in other materials such as Pb, Zn and AL . A conclusion was maded: the resistance of materials can disappear when the critical conditions (critical current Ic, critical magnetic field Hc, critical temperature Tc, etc.) are simultaneously met. This is called zero resistance phenomenon of superconductivity.At low temperature, with the disappearance of resistance, the material appears a new state, which is called superconducting state. The material is called superconducting material, the temperature when the resistance disappear is called the critical temperature ,or transition temperature. The resistance of the superconductor is 1010 times lower than its resistance at 0°C. The resistivity of the superconductor is less than 10-23Ω·cm.While the resistivity of the copper is1.6×10-6Ω·cm at 0 ℃.So the resistance of the superconductor can be regarded as zero.2.2 Meissner effectBefore 1933,people equalled superconductor with perfect conductor.Perfect conductor is an illusion of the ideal body,which has no resistance.There is no electric field in perfect conductor,neither is time-varying magnetic induction intensity.That is, the magnetic field inside the perfect conductor is kept as the moment the perfect conductor loss resistance.We can consider it as the magnetic flux distribution is "frozen" in the sample,while the change of external magnetic field can not change the magnetic pass distribution inside the frozen sample.Until 1933, two German physicists, Olsenfeld and Meissner discovered Meissner effect.When they measure the magnetic field distribution inside the tin single crystal ballsuperconductor,a phenomeno occurred their attention. In the magnetic field,If cool the metal into the superconducting state, the superconducting magnetic lines will discharge in a sudden, and the magnetic induction line can not pass through its body. That means once superconducting material entered into the superconducting state, the intensityin side the superconductor magnetic field is constant to zero. No matter the conductor is the first magnetic field after cooling, or the first cooling after the magnetic field, as long as it becomes the superconducting state, the superconductor will be all the magnetic induction line from the body. This complete diamagnetism of the superconductor is another essential properity of the superconductor.2.3 Isotope effectThe critical temperature(Tc) of the superconductor is related to its isotope mass(M). The higher the mass, the lower the critical temperature.This phenomeno is called the isotope effect[5]. Take mercury for example, a mercury isotope with an atomic weight of 199.55 has a TC of 4.18 , however a mercury isotope of 203.4 has a TC of 4.146.2.4 Josephson effectFirst, introduce the Tunneling Effect. Between two pieces of metal ,sandwichs very thin insulating layer (the thickness is about several nanometers, such as oxide film).When the potential energy is applied to form a potential barrier V, the fine particles can pass through the potential barrier V from the insulating layer side to reach the other side in the condition of E <V . This physical phenomenon is called the Tunneling Effect .Then, introduce the Josephson Effect. The Josephson effect, also known as the tunneling effect or the barrier penetration.It is a quantum effect determined by the fluctuation of the microscopic particles. According to classical mechanics analysis, the particles can not pass through the barrier,as the barrier is higher then particles. But according to quantum mechanical analysis , the particles have a certain probability to go through the barrier, in the other side of the barrier. Because according to the quantum mechanical analysis ,there are reflection near the barrier ,as well as wave function. The Josephson effect is a quantum effect of the microscopic world, which is impossible to see in macroscopic world. To microscopic particles, quantum mechanics proves that it can pass through the barrier, which is exactly confirmed by studies. Under normal circumstances, the tunneling probability of tunneling effect is very small. It can be considered that the tunneling effect does not affect the macroscopic effect.3.Superconducting Materials and Applications3.1 Classification of superconducting materialsAccording to their critical transition temperature, superconducting materials can be divided into low-temperature superconducting materials and high-temperature superconducting materials.3.1.1 low-temperature superconducting materialsLow-temperature superconducting materials (Tc <30K),working at liquid helium’s temperature and is divided into metals, alloys and compounds. Nb has practical value in low-temperature with a Tc of 9.3 K. Nb-based materials have been made into film[6],used in weak current. Nb-based materials are binary or ternary alloys composed of β-phase solid solution, Tc is above 9 K. In the strong electromagnetic field, NbTi superconducting materials are used as high-energy physics accelerator, detectors, plasma magnetic confinement, superconducting energy storage, superconducting motor and medical magnetic resonance human imager, etc . low-temperature equipment made of Nb and NbN film, has been used for military and medical detection of very weak electromagnetic signals. However,because of materials must be used in liquid helium temperature, the cost is high . So its application is limited.3.1.2 High-temperature superconducting materialsHigh-temperature superconducting material is the superconducting material whose critical temperature is above 30K (now usually be considered more than 77K) and the resistance is close to zero.Because the superconducting material has zero resistance and complete diamagnetism, it only needs very little electric energy, and obtain stable strong magnetic field. It can be used to manufacte AC superconducting generators. Superconducting coil magnets can increase the generator's magnetic field to 50,000 to 60,000 gaussian and no energy loss. More important, the single power generation capacity increased 5 to 10 times than conventional generators,which is up to 1 MW. While the volume is reduced bya half, the whole weight reduction 1/3,and the efficiency increased by 50 %.3.2 Applications of superconducting materialsThe zero-resistance effect allows the current to flow through the superconductor without heat loss, and the current can form a strong current in the wire without any resistance, resulting in a super-strong magnetic field. There are three main usage of superconducting technology: superconducting cables, superconducting generators, superconducting transformers and superconducting current limiter,and so on. The United States is the first country to develop and use superconducting cable, in 1992. Superconducting cable mainly composed by the cable body, terminal and low temperature refrigeration device.Nondestructive testing is a widely used detection technology.SQUID non-destructive testing technology. SQUID can detect small changes in the field, increase the depth of detection, improve the resolution, and can determine the internal defects and corrosion of multi-layer alloy conductor materials. This is what other means of detection can notfinish. SQUID is used to detect internal corrosion in industry. And in military, it can be used to detect mines or submarines.Now, scientists are studying superconductivity for its application on magnetic suspension trains and superconducting bearings.Superconducting suspension trains are suspended with the track. There are not any firction between rail and the train. Maglev train is easy to repair. The energy consumption is only half of a car. The noise is only 65 decibels.And the speed is 300 km/h. It uses current power to drive, does not emit pollution, is a green means of transport.Magnetic bearings are mainly used in high-speed rotation of the site. Using the complete diamagnetism of the superconductors, the frictionless suspension bearings can be made. Which avoids mechanical wear, reduces energy consumption and noise, and has the advantages of maintenance-free, high speed, high precision and good dynamic characteristics. Magnetic bearings can be applied to high-speed centrifuge, flywheel energy storage, aerial gyroscope and other high-speed rotation system.4.ConclusionThe research of superconducting materials is an emerging science and technology in the world today. As superconducting materials can affect many important areas of human life, the material scientists are competing to explore its structure and performance, in order to find a high critical temperature of superconducting materials. It’s believed that superconductivity and it’s applications will become the core technology of the 21st century, to benefit all mankind.Reference[1] 郭奕玲，沈慧君. 物理学史. 北京：清华大学出版社，1997.[2] 刘兵. 著名超导物理学家列传[M]. 北京：北京大学出版社，1988:107-116.[3] 马龙飞，宫成等.高温超导电缆的发展与趋势 [J]. 电子技术应用，2014，（z1）.[4] 马文蔚，苏惠惠. 物理学原理在工程技术中的应用[M]. 北京：高等教育出版社，1992.[5] 肖军. 超导现象及同位素效应的理论解释.[6] 冯瑞华，姜山. 超导材料的发展与研究现状[J]. 超导技术，2007:520-526.。

高温超导材料物理研究

高温超导材料物理研究IntroductionSuperconductors, materials that can conduct electricity with essentially zero resistance, have fascinated scientists and engineers for over a century. However, traditional superconductors require extreme cooling, typically to temperatures close to absolute zero, making their practical applications quite limited. In the mid-1980s, high-temperature superconductors were discovered, revolutionizing the field of low-temperature physics. These materials exhibit superconductivity at relatively higher temperatures, making them potentially useful in a variety of engineering applications. In this article, we will discuss the physical properties and ongoing research efforts in the field of high-temperature superconductors.Types of High-Temperature SuperconductorsThere are several different types of high-temperature superconductors, each with its peculiar properties and characteristics. The most common types are cuprates, iron-based superconductors, and fullerides.Cuprates are copper-based oxides that exhibit high-temperature superconductivity. These materials are layered and are highly anisotropic in their electronic properties.Iron-based superconductors (also known as "FeSCs") were first discovered in 2008 and are comprised of metal Fe atoms arranged in a certain crystal structure. The electronic structure of these materials is more three-dimensional than cuprate superconductors, which could lead to different types of potential applications.Fullerides are molecular compounds composed of carbon atoms arranged in a hollow spherical shape, similar to a soccer ball. These materials can act as electron acceptors and could redefine the field of organic semiconductors.Physical PropertiesSuperconductivity is characterized by the fact that electrons can move through the material without resistance. This unusual property of high-temperature superconductors arises from their electronic band structure, or in other words, the way electrons move and interact with each other within the material. The essential factors that determine the superconducting properties of these materials are the strength of the electron-electron interactions, the density of electronic states near the Fermi level, and the topology of the electronic energy band structure.Another crucial property of high-temperature superconductors is their vortex state. When a magnetic field is applied to the superconductor, vortices form, which can hinder the flow of electric current through the material. Understanding the physics of vortexdynamics is central to optimizing the performance of high-temperature superconductors for different applications.Ongoing ResearchThe fundamental mechanisms behind high-temperature superconductivity remain under intense research, involving theoretical studies, simulations, and experiments. One significant area of recent research is the impact of doping in high-temperature superconductors. Doping refers to the controlled introduction of impurities into the material to change its electronic properties. Doping can be used to modify the electronic properties of the material, such as its density of states and electronic band structure.Another area of current research is the use of high-pressure synthesis to modify the electronic structure of these materials. Applying pressure to the sample can change how the atoms are arranged in the material, thus altering its electronic properties.Finally, the development of new methods for manipulating vortices in high-temperature superconductors is an active area of research, including the use of artificial pinning centers and magnetic field modulation.ApplicationsHigh-temperature superconducting materials have the potential for a wide range of applications, such as power transmission lines, MRI machines, and High-energy particle accelerators. Other potential usesinclude advanced computing and communication, quantum computing, and electric power storage.ConclusionThe discovery of high-temperature superconductors has opened a new frontier in the field of condensed matter physics. Understanding the physical properties and mechanisms behind these materials is central to unlocking their full potential for various applications. The ongoing research efforts in this field are expected to yield exciting discoveries in the coming years, making high-temperature superconductors a fascinating field of study.。

超导电力技术的发展与超导电力装置的性能检测

超导电力技术的发展与超导电力装置的性能检测胡　毅1,唐跃进2,任　丽2,蔡　炜1,陈轩恕1,石　晶2,陈　磊2,张翌晖2,郭　芳2(1.国网武汉高压研究院,武汉430074;2.华中科技大学超导电力研究中心,武汉430074)摘　要:充分利用国内各种优势资源开展超导电力技术的研究与开发,对于提高我国电力设备行业在国际市场上的竞争力及电力系统的技术经济性能均有重大的意义。

基于对国内外超导电力技术及超导电力装置的充分调研,概括了超导电力技术的研究现状,归纳了超导电力技术中的关键课题,即超导电力装置;超导电力系统的协调运行与系统理论研究;超导电力系统中的在线监测与控制策略;超导电力相关学科的基础研究。

指出了未来超导电力装置的研究重点,并给出了具有代表性的超导电力装置的试验、检测内容和性能检测方法,迈出了超导电力装置性能检测方法与规程研究的第一步。

关键词:超导电力技术;电力系统;超导电缆;超导磁储能系统;超导变压器;超导限流器中图分类号:TM26文献标志码:A 文章编号:100326520(2007)0720001208基金资助项目:国网武汉高压研究院科研基金(062SH080)。

Project Supported by Scientific Research Foundation of Wuhan High Voltage Research Institute of SGCC (062SH080).Development of Superconducting Pow er T echnology and Performance T estof Superconducting Pow er DeviceHU Y i 1,TAN G Yue 2jin 2,REN Li 2,CA I Wei 1,CH EN Xuan 2shu 1,SH I Jing 2,CH EN Lei 2,ZHAN G Yi 2hui 2,GUO Fang 2(1.Wuhan High Voltage Research Instit ute of SGCC ,Wuhan 430074,China ;2.R &D Center of Applied Superconductivity ,Huazhong Univercity of Science and Technology ,Wuhan 430074,China )Abstract :Application of superconducting power technology to conventional power industry is the inevitable step in the development of power industry.The development strategy of superconducting power technology ,f ull utilization of domestic dominant resource and establishment of superconducting power experiment and research base ,that has considerable significance in the continual development of national economy ,were reviewed.The present research state and key subjects in superconducting power technology were summarized.And ,the focal research points in fu 2ture superconducting power areas was presented.Finally ,the test items of some typical superconducting power de 2vices was discussed as the first step of the research for performance test and standard of superconducting power de 2vices.K ey w ords :superconducting power technology ;power system ;superconducting cable ;SM ES ;superconducting transformer ;SFCL0　引　言随着电力系统容量的增大、系统结构复杂化以及电力用户对供电品质要求的提高,电力系统已突显出了若干技术难题,如电力安全、高密度供电、高品质供电、高效率输送电等[1]。