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。

然而状况并非总是这么完美，对于某些超导体，存在两个临界温度，记为H1和H2。

即二型超导体，已发现的超导元素中，只有钒、铌和钽属于第二类，其他元素均属第一类。

然而大多数超导合金和化合物则属于第二类：它们的区分在于：第一类超导体的京茨堡-朗道参量,超导-正常相的界面能为正；而第二类超导体，界面能为负。

单一抗磁性原理并不能解释量子锁定，因为抗磁性只能是超导体悬浮起来，不能造成锁定的效果。

事实上，能够产生量子锁定现象的都是第二类超导体。

对于第二类超导体，在H1与H2之间，会有部分磁感线从超导体中穿过。

由于体内存在晶体缺陷而呈现不可逆的特性。

当外磁场从零开始增大但小于H c1时,超导体处于迈斯纳态。

当H>H c1时，磁场以磁通线的形式穿透体内。

但缺陷的存在对磁通线的穿透造成阻力，因此超过H c1时，磁化强度继续增大。

当H>H p时, 则随磁场的增大而它减小。

直至H c2时,磁化强度才等于零。

当磁场从高于H c2下降时,缺陷同样阻碍磁通排出，故磁化曲线上出现磁滞现象，以致零磁场时有剩余磁矩，称为俘获磁通。

晶阵缺陷的存在，阻碍着磁通线的运动。

因此，可以把它们看作是一些对磁通线运动产生钉扎作用的钉扎体，也称为磁通钉扎中心。

钉扎作用的强弱以钉扎力F p的大小来表示。

当温度高于绝对零度时，由于热激活的存在，磁通线总是有一定的几率从一个钉扎中心迁移到另一个钉扎中心，这种磁通线发生跳跃式的无规运动叫做磁通蠕动。

然而，超导体不“喜欢”这样的磁通蠕动，因为这样的移动会消耗能量，会破坏超导体的状态，于是超导体将这些穿越其中的磁感线锁定了，将这些磁通量子锁定在原地，于是自己也就被锁定在原地了。

量子锁定与量子悬浮或者磁力悬浮反重力悬浮之间的区别就在于量子锁定是真正意义上的锁定。

不需要方向性的限制。

任何方向取向都满足锁定的条件。

而且锁定之后的牢固程度也是悬浮无法达到的。

锁定强度大概可以维持自身7万倍的离。

直观的描述这种力，半径5cm，厚3mm的高温超导材料：yttrium barium copper oxide（YBa2Cu3O7-x）。

它的相变温度在 -185.15℃左右，可以承受的压力足以支撑起一辆小型汽车。

量子悬浮使得超导体的应用摆脱原来的斥力作用，上升到悬浮的新层面。

现在的磁悬浮列车，都是借助超导线圈在磁场中收到的排斥力完成悬浮，而通过量子悬浮锁定，不但可达到原有的列车在磁性轨道上方悬浮的要求，甚至可以悬浮在磁性轨道下方。

而且这种悬浮相比于原有的悬浮，对于轨道的平整度低了许多。

原有的磁悬浮列车，悬浮高度只有10mm，于是轨道就要求非常的平整，而在实验室中较低的磁场强度下很小尺寸的超导体都可以达到40mm的悬浮，这就大大降低了铺设轨道的成本以及工艺难度。

这对于交通工具都是一个里程碑式的突破。

除了交通工具以外，量子悬浮锁定还可以被用来制造超导轴承，用磁性物质制作轴承的外圈，用超导体制作轴承中间的转子，这样转子在轴对称的磁场中就会锁定在中心，与外圈没有摩擦，从而将损耗降到最低。

这一切的应用设想都建立在高温超导甚至常温超导的普及，虽然这个普及还离今天非常的遥远，但是有理由相信量子悬浮锁定在未来具有不可估量的发展潜力。

参考文献：Chaotic movement of vortices in superconductors of high-Tc superconducting maglev system at a high speed超导加盟未来战争-国防-2002年第8期(2）超导转子旋转驱动装置的设计-光学精密工程-2010年第1期(6)三维介观超导环涡旋态的研究-低温与超导Title :Superconducting quantum state of the locklxyAbstract: the history of superconductivity from discovery has been more than 100 years. From the phenomenon of superconductivity and quantum mechanics together, people don't just focus on the nature and causes of the phenomenon, but the phenomenon of superconductivity. The BCS theory, the Manas effect, quantum mechanics makes people superconductivity has been a qualitative leap. Constantly updated withthe critical temperature. And therefore found many new phenomena.Keywords: superconducting quantum mechanical phenomena of anti magnetic emerging technologyIn 1911 the Holland physicist Camlin Onis found that the mercury temperature completely lost their resistance in the vicinity of 4K, decades scientists continue to discover multipleelement or alloy at a specific temperature resistance mutation of 0 phenomenon, called superconducting phenomenon. However. Superconducting phenomenon includes two aspects, usually known as the zero resistance, however related electromagnetic phenomena that we, superconductors have a magnetic effect of special.A small piece of superconductor is cooled to a critical temperature, above a magnet, found superconductor suspended in the magnet, and moving with the magnet moving even flip, is locked in the magnet, we call this phenomenon called quantum levitation or quantum locking. The so-called Meisner effect.Cause every physical phenomena are so that we can not help but ask behind. This is how the special magnetic effect. Quantum mechanics respond, superconductors exhibit diamagnetic completely at the critical temperature. Superconductor once in the superconducting state, the magnetic flux in vivo will all be excreted, magnetic induction intensity constant is zero, regardless of theconductor is first cooled magnetic field or magnetic field, after cooling, as long as access to the superconducting state, superconductor to put all the magnetic flux from in vitro. The magnetic field cannot enter or (literally) widely exists in superconductors, which is another basic properties of superconductor. Through the ring current spontaneous rejection through the internal conductor of magnetic induction line. When the superconductor in a magnetic field, because of the action of the electric induction, the superconductor surface induced current I (permanent current), in superconductors, induction current I excitation magnetic field and external magnetic field is equal and opposite, cancel each other out. Later, people also made such an experiment, in a shallow tin plate, placed in a small permanent magnet magnetic strong, then the temperature is lowered, the tin appeared superconductivity. Then you can see, the small magnet unexpectedly left tin plate surface, floating in the air to rise, to maintain a certain distance with the tin pan, then hanging motionless. This is because the perfect diamagnetism of superconductor, which cannot penetrate the superconductor magnet magnetic field lines, magnetic field distortion, will produce an upward buoyancy.But the situation is not always so perfect, for some superconductors, there are two critical temperature, denoted as H1 and H2. The two type of superconductor, superconducting elements have been discovered, only vanadium, niobium and tantalum belong to the second class, the other elements are first class. However, most of the superconducting alloys and compounds belong to the second class: the difference between them is that: the first type superconductor Ginzburg Landau parameter, superconducting normal phase interface for it; and the second superconductors, interfacial energy is negative.Single anti magnetic principle does not explain quantum locking, since the anti magnetic only superconductor suspended, cannot cause locking effect. In fact, can produce quantum locking phenomenon is a superconductor of the second kind. For the second class of superconductors, between H1 and H2, will be part of magnetic induction line through the superconductors. Due to the body in crystal defect and showed characteristics of irreversible. When the external magnetic field increases but less thanHc1 from zero, the superconductor in the Meisner state. When H> Hc1 when the magnetic flux lines, in the form of penetration in vivo. But the existence of defects on the flux penetration resistance caused by, so is more than Hc1, the magnetization increases. When H> Hp, with the increase of the magnetic field while it decreases. Until Hc2, magnetization to zero. When the magnetic field from more than Hc2 decline, defects also hampering the flux expulsion, hysteresis phenomenon of the magnetization curve, so that the zero magnetic field when the remanent magnetization,called the trapped flux.Crystal lattice defects, hindering the flux motion. Therefore, they can be regarded as some of the pinning effect of the flux line pinning body movement, also known as flux pinning center. The strength of the pinning effect on pinning force Fp to express the size of. When the temperature is higher than the absolute zero, due to thermally activated flux lines exist, there is always a chance from a pinning centers migrated to another pinning centers, the flux jump random motion is called the flux creep.However, superconductors do not "love" flux creep like this, because this movement can consume energy, will destroy the superconducting state, so the superconductor will these through the magnetic induction line locked, the flux quantum locked in place, so you will be locked in place.Quantum locking and quantum levitation or magnetic levitation suspension against gravity difference lies in quantum lock is locked in the true sense of the. Don't need direction restriction. Any direction all meet the lock condition. And the firm degree after lock is suspended cannot reach. The locking strength can probably sustain itself 70000 times from the. Intuitive description of this force, the radius 5cm, high temperature superconducting material thickness of 3mm: yttrium barium copper oxide (YBa2Cu3O7-x). The phase transition temperature of -185.15 ℃ in Can withstand the pressure enough to support a small car.Quantum levitation makes application of superconductors from the repulsion of the original, rising to new levels of suspended. Maglev train now, is the repelling force received by a superconducting coil in a magnetic field by quantum complete suspension, suspension locking, can achieve the original train on suspended magnetic track above requirements, and even can be suspended in a magnetic track.And the suspension compared to the original suspension, for the formation of the track is much lower. The original of the maglev train, suspension height is only 10mm, so the orbit requires very smooth, and the superconductor magnetic field strength in the laboratory of the lower small size can be achieved 40mm suspension, which greatly reduces the cost and difficulty of track laying process. This is a milepost type breakthrough for transportation. In addition to transport, quantum suspension locking can also be used to make superconducting bearings, making the outer ring of the bearing with magnetic materials, superconductors fabricated rotor bearing in the middle, so that the rotor in the axial symmetric magnetic field will be locked in the center, no friction and the outer ring, thus the loss to a minimum. The popularity of all this application ideas are based on high temperature superconducting and normal temperature superconducting, although thispopularity is also very far from today, but there is reason to believe that quantum levitation development potential immeasurable locked in the future.Reference.Chaotic movement of vortices in superconductors of high-Tc superconducting maglev system at a high speedFuture war - defense -2002 superconducting joined eighth years period (2)The design of rotating driving device superconducting rotor -2010 optics and precision engineering first (6)Low temperature and Superconductivity Research three-dimensional mesoscopic superconducting ring vortex state。