Paltiel Y, Zeldov E, Myasoedov YN, Shtrikman H, Bhattacharya S, Higgins MJ, Xiao ZL, Andrei EY, Gammel PL, Bishop DJ
Department of Condensed Matter Physics, The Weizmann Institute of Science, Rehovot, Israel.
Nature. 2000 Jan 27;403(6768):398-401. doi: 10.1038/35000145.
The magnetic flux line lattice in type II superconductors serves as a useful system in which to study condensed matter flow, as its dynamic properties are tunable. Recent studies have shown a number of puzzling phenomena associated with vortex motion, including: low-frequency noise and slow voltage oscillations; a history-dependent dynamic response, and memory of the direction, amplitude duration and frequency of the previously applied current; high vortex mobility for alternating current, but no apparent vortex motion for direct currents; and strong suppression of an a.c. response by small d.c. bias. Taken together, these phenomena are incompatible with current understanding of vortex dynamics. Here we report a generic mechanism that accounts for these observations. Our model, which is derived from investigations of the current distribution across single crystals of NbSe2, is based on a competition between the injection of a disordered vortex phase at the sample edges, and the dynamic annealing of this metastable disorder by the transport current. For an alternating current, only narrow regions near the edges are in the disordered phase, while for d.c. bias, most of the sample is in the disordered phase--preventing vortex motion because of more efficient pinning. The resulting spatial dependence of the disordered vortex system serves as an active memory of the previous history.
II型超导体中的磁通线晶格是研究凝聚态流动的一个有用系统，因为其动力学性质是可调的。最近的研究显示了一些与涡旋运动相关的令人困惑的现象，包括：低频噪声和缓慢的电压振荡；与历史相关的动态响应，以及对先前施加电流的方向、幅度、持续时间和频率的记忆；交流电下涡旋迁移率高，但直流电下无明显涡旋运动；以及小直流偏置对交流响应的强烈抑制。总体而言，这些现象与当前对涡旋动力学的理解不相符。在此，我们报告一种能解释这些观察结果的通用机制。我们的模型源自对NbSe2单晶中电流分布的研究，基于样品边缘无序涡旋相的注入与输运电流对这种亚稳态无序的动态退火之间的竞争。对于交流电，只有边缘附近的狭窄区域处于无序相，而对于直流偏置，大部分样品处于无序相——由于更有效的钉扎作用而阻止涡旋运动。无序涡旋系统产生的空间依赖性充当了对先前历史的主动记忆。
