Department of Physics, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
Nano Lett. 2017 Aug 9;17(8):4604-4610. doi: 10.1021/acs.nanolett.7b00977. Epub 2017 Jul 10.
Despite the established knowledge that crystal dislocations can affect a material's superconducting properties, the exact mechanism of the electron-dislocation interaction in a dislocated superconductor has long been missing. Being a type of defect, dislocations are expected to decrease a material's superconducting transition temperature (T) by breaking the coherence. Yet experimentally, even in isotropic type I superconductors, dislocations can either decrease, increase, or have little influence on T. These experimental findings have yet to be understood. Although the anisotropic pairing in dirty superconductors has explained impurity-induced T reduction, no quantitative agreement has been reached in the case a dislocation given its complexity. In this study, by generalizing the one-dimensional quantized dislocation field to three dimensions, we reveal that there are indeed two distinct types of electron-dislocation interactions. Besides the usual electron-dislocation potential scattering, there is another interaction driving an effective attraction between electrons that is caused by dislons, which are quantized modes of a dislocation. The role of dislocations to superconductivity is thus clarified as the competition between the classical and quantum effects, showing excellent agreement with existing experimental data. In particular, the existence of both classical and quantum effects provides a plausible explanation for the illusive origin of dislocation-induced superconductivity in semiconducting PbS/PbTe superlattice nanostructures. A quantitative criterion has been derived, in which a dislocated superconductor with low elastic moduli and small electron effective mass and in a confined environment is inclined to enhance T. This provides a new pathway for engineering a material's superconducting properties by using dislocations as an additional degree of freedom.
尽管已经知道晶体位错会影响材料的超导性能，但电子与位错相互作用的确切机制长期以来一直缺失。位错作为一种缺陷，预计会通过破坏相干性来降低材料的超导转变温度 (T)。然而，从实验上看，即使在各向同性的 I 型超导体中，位错对 T 的影响也可能降低、增加或几乎没有影响。这些实验结果仍未得到解释。尽管在有杂质的超导中各向异性配对可以解释杂质引起的 T 降低，但由于位错的复杂性，在这种情况下，尚未得出定量的一致结果。在这项研究中，我们通过将一维量子化的位错场推广到三维，揭示了实际上存在两种不同类型的电子与位错相互作用。除了通常的电子与位错的势能散射之外，还有另一种相互作用，它是由位错的量子模式——位错子引起的，会导致电子之间产生有效的吸引力。因此，位错对超导性的作用被澄清为经典和量子效应之间的竞争，这与现有的实验数据非常吻合。特别是，经典和量子效应的存在为半导体 PbS/PbTe 超晶格纳米结构中位错诱导超导性的虚幻起源提供了一个合理的解释。我们已经推导出一个定量的判据，其中具有低弹性模量、小电子有效质量和受限环境的位错超导体更倾向于增强 T。这为通过将位错用作附加自由度来设计材料的超导性能提供了一条新途径。
