Two coexisting vortex phases in the peak effect regime in a superconductor
Two coexisting vortex phases in the peak effect regime in a superconductor
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DOI：
10.1038/35054512
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发表时间：
2001-02-01
期刊：
影响因子：
64.8
通讯作者：
Bhattacharya, S
中科院分区：
文献类型：
--
作者：
Marchevsky, M;Higgins, MJ;Bhattacharya, S
第二类超导体如NbSe 2的涡旋相的临界电流在超导体到正常金属的转变附近显示出惊人的异常。它不是平滑地归零，而是在过渡处消失之前，突然反弹到一个尖锐而明显的最大值。这种违反直觉的现象被称为峰值效应（1-3），40年来一直是一个未解决的问题。这里我们使用扫描交流。霍尔显微镜观察NbSe 2中临界电流的真实空间分布。我们表明，在峰值效应制度两个不同的涡旋物质相本质上不同的钉扎强度共存的宏观尺度上。两相混合物的组成和一相到另一相的转变是造成历史效应（4-6）和异常电压响应（4，5）的原因，当外部参数如温度、磁场或传输电流变化时，通常会看到这些效应。我们认为，所观察到的相共存，事实上，无序驱动的非热相变的标志。
The critical current in the vortex phase of a type-II superconductor such as NbSe2 displays a striking anomaly in the vicinity of the superconductor-to-normal-metal transition. Instead of going to zero smoothly, it rebounds to a sharp and pronounced maximum, just before vanishing at the transition. This counter-intuitive phenomenon, known as the peak effect(1-3), has remained an unsolved problem for 40 years. Here we use a scanning a.c. Hall microscope to visualize the real-space distribution of the critical current in NbSe2. We show that in the peak-effect regime two distinct vortex-matter phases with intrinsically different pinning strengths coexist on a macroscopic scale. The composition of the two-phase mixture and the transformation of one phase into another are responsible for the history effects(4-6) and anomalous voltage response(4,5) commonly seen when external parameters such as temperature, magnetic field or transport current are varied. We argue that the observed phase coexistence is, in fact, the hallmark of a disorder-driven non-thermal phase transition.