Enhancement of superconductivity at structural defects in high-temperature superconductors
Enhancement of superconductivity at structural defects in high-temperature superconductors
复制标题
高温超导体结构缺陷处超导性的增强
DOI：
10.1103/physrevb.56.6213
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发表时间：
1997
影响因子：
3.7
通讯作者：
E. Pashitskii
中科院分区：
文献类型：
--
作者：
A. Gurevich;E. Pashitskii
结果表明，无论超导的微观机制和缺陷的纳米结构如何，高温超导体中结构缺陷周围的长程应变场都可以在明显高于体临界温度 T{sub c0} 的温度下产生局部超导域。该效应是由于 T{sub c0} 对高 T{sub c0} 超导体的压力和空穴浓度特性具有很强的非单调依赖性。我们计算了刃位错、小角度晶界和亚稳态线位错阵列的 T{sub c} 增量 {Delta}T{sub c}=T{sub c}{minus}T{sub c0}，同时考虑了 ab 平面中 T{sub c} 的各向异性应变依赖性。晶界上的超导状态是由位于边缘位错周期链上的超导域的邻近耦合产生的。在这种情况下，{Delta}T{sub c}({theta})随着取向差角{theta}而减小，在临界角{theta}{sub 0}处消失，该临界角是由T{sub c}的应变场增强和位错核心中超导性的抑制之间的竞争决定的。我们计算了 T{sub c0}{lt}T{lt}T{sub c} 处沿晶界网络的磁化率和临界电流。对于由塑性变形引起的亚稳态位错阵列，应变引起的 T{sub c} 增强比以前的晶界更加明显，并且发生在比相干长度大得多的宏观域中。这些域中的局部残余应变足够强，足以揭示 T{sub c} 的绝对最大值，这在静水压力实验中可能看不到。讨论了缺陷应变场的成分变化以及 T{sub c} 变化对磁通钉扎和磁粒度的影响。 {版权} {ital 1997} {ital 美国物理学会}« 更少
It is shown that long-range strain fields around structural defects in high-temperature superconductors can give rise to localized supercoducting domains at temperatures noticeably higher than the bulk critical temperature T{sub c0}, regardless of the microscopic mechanism of superconductivity and the nanostructure of the defects. The effect is due to the strong nonmonotonic dependence of T{sub c0} on pressure and hole concentration characteristic of high-T{sub c} superconductors. We calculated the T{sub c} increase {Delta}T{sub c}=T{sub c}{minus}T{sub c0} for edge dislocations, low-angle grain boundaries, and metastable linear dislocation arrays, taking into account the anisotropic strain dependence of T{sub c} in the ab plane. The superconducting state on the grain boundaries results from the proximity coupling of superconducting domains localized on the periodic chain of edge dislocations. In this case {Delta}T{sub c}({theta}) decreases with the misorientation angle {theta}, vanishing at the critical angle {theta}{sub 0} determined by the competition between the strain fields enhancement of T{sub c} and the suppression of superconductivity in the dislocation cores. We calculated the magnetic susceptibility and the critical current along the grain boundary network at T{sub c0}{lt}T{lt}T{sub c}. For metastable dislocation arrays caused by plastic deformation, the strain-induced T{sub c} enhancement is much more pronounced than formore » grain boundaries and occurs in macroscopic domains much larger than the coherence length. The localized remanent strains in these domains can be strong enough to reveal the absolute maximum of T{sub c} which may not be seen in hydrostatic pressure experiments. The compositional change in the strain fields of defects and the implications of the T{sub c} variations on flux pinning and magnetic granularity are discussed. {copyright} {ital 1997} {ital The American Physical Society}« less