Varieties of dynamics in a disordered flux-line lattice
Varieties of dynamics in a disordered flux-line lattice
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DOI：
10.1016/0921-4534(95)00704-0
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发表时间：
1996-02-01
期刊：
影响因子：
1.7
通讯作者：
Bhattacharya, S
中科院分区：
文献类型：
--
作者：
Higgins, MJ;Bhattacharya, S
磁通线晶格 (FLL) 的动力学已在各向异性超导体 2H-NbSe2 中进行了研究，其中钉扎极弱（临界电流/脱配电流类似于 10(-6)），晶格结构良好，并且在稍低于 H-c2 时会出现强大的“峰值效应”。 FLL 刚性的强 H 依赖性可用于探索相互作用主导和无序主导动力学之间的交叉。当晶格随着接近超导正常相边界而软化时，观察到三种不同类型的动力学，分别描述弹性流、塑性流和流体流。幂律行为 V 类似于 (I-I-c)(beta)，相当好地描述了弹性流动和流体流动（具有不同 beta）的 I-V 曲线，但不适用于塑性流动。后者主导中间状态，其中出现峰值效应，并伴随着与 FLL 撕裂相关的 I-V 曲线的质变。在这种情况下，在电流相关的微分电阻中观察到“指纹现象”，描述了给定样品中“块”或细丝脱钉的特定顺序。在大驱动力下，钉扎造成的紊乱不太明显，动态产生的缺陷会愈合，并且恢复几乎无缺陷的相干运动。在一些样本中，该状态下运动开始时的 I-V 曲线变得不连续且滞后，就像一阶跃迁一样。构建了描述各种动力学状态的“非平衡相图”。时间平均速度相关长度表征了移动 FLL 的空间不均匀性，从而区分了各种动态状态。这些动力学现象与铜酸盐超导体中热力学相变的现象进行了比较和对比。
Dynamics of a flux-line lattice (FLL) has been studied in the anisotropic superconductor 2H-NbSe2, where pinning is extremely weak (critical current/depairing current similar to 10(-6)), the lattice is well-formed and a robust ''peak effect'' occurs slightly below H-c2. The strong H dependence of the rigidity of the FLL is used to explore the crossover between interaction-dominated and disorder-dominated dynamics. Three distinct types of dynamics, describing elastic flow, plastic flow and fluid flow, respectively, are observed as the lattice softens with the approach to the superconducting-to-normal phase boundary. A power-law behavior, V similar to (I-I-c)(beta), describes the I-V curves for both elastic and fluid flow (with different beta) reasonably well, but not for plastic flow. The latter dominates the intermediate regime, where the peak effect occurs, and is accompanied by qualitative changes in the I-V curves related to tearing of the FLL. In this regime, a ''fingerprint phenomenon'' is observed in the current-dependent differential resistance describing a specific sequence of depinning of ''chunks'' or filaments in a given sample. At large driving forces, the disorder due to pinning is less significant, the dynamically generated defects heal and a nearly defect-free coherent motion is recovered. In some samples, the I-V curves at the onset of motion in this regime become discontinuous and hysteretic as in first-order transitions. A ''non-equilibrium phase diagram'' describing various regimes of dynamics is constructed. A time-averaged velocity correlation length characterizes the spatial inhomogeneity of a moving FLL and thus distinguishes between the various dynamical regimes. These dynamical phenomena are compared and contrasted with phenomena attributed to thermodynamic phase transitions in the cuprate superconductors.