高温超导体磁通动力学和混合态相图(Ⅰ)

Flux dynamics and vortex phase diagram of cuprate superconductors(Ⅰ)

文章简要介绍了高温超导体磁通动力学和混合态物理在过去十余年的发展.高温超导体由于其自身的一些特点,使得它与常规超导体相比较拥有极其丰富的相图,磁通动力学也表现出了非常丰富的研究内容,很多新的概念被提出,新的现象被观察到.比如说涡旋玻璃态,集体钉扎和蠕动,磁通格子的一级和二级熔化相变,布拉格玻璃,峰值效应,二维涡旋饼态,Josephson磁通运动等等,均是在高温超导体发现之后提出来的新的概念或新发现的现象.有些研究结果目前尚无定论,如关于涡旋玻璃态存在与否的争论至今仍然在进行,但是这些研究内容无疑会大大促进超导物理的发展.高温超导体磁通动力学纷繁复杂的研究内容可以归结为三个相互关联的数字:G inzburg数(Tc/H2cε3ζ)2/2,量子电阻Qu=(e2/)(ρn/εζ),和临界电流的比值jc/j0,这里ζ是相干长度,Hc是热力学临界磁场,ε是有效质量的各向异性度,nρ是正常态电阻率,jc是零温临界电流,j0是拆对临界电流.对于高温超导体前两个数值(G inzburg数和量子电阻)很大,而临界电流比值较小,因此导致有强的热涨落和量子涨落,以及很强的磁通运动行为(对应小的实测临界电流).磁通动力学的研究从更深层次影响超导体的临界电流问题和强电应用的发展,最后简要地介绍了这方面的情况.

A brief introduction to the development of flux dynamics and the vortex phase diagram of high temperature superconductors over the past decade is presented. Due to its intrinsic properties, high-Tc cuprates exhibit very rich and complex characteristics. Many new concepts have thus been proposed and new phenomena observed, including the vortex glass state and transition, collective pinning and creep, first order and second order melting of the vortex matter, Bragg glasses, the peak effect, 2D vortex pancakes, Josephson vortex motion, and so forth. Many of the concepts are still under debate, In the complex vortex phase diagram, the system is characterized by three important parameters, i. e. , the Ginzburg number, quantum resistivity, and the critical current density ratio. For euprate superconductors, the former two parameters are one to two orders of magnitude larger than those in their conventional counterparts, while the last parameter is about one order of magnitude smaller. Investigations on the flux dynamics in cuprates will greatly help our understanding of the limitations on large scale application.