过渡金属二卤化物中的非常规栅极诱导超导电性

Thibault Sohier, Marco Gibertini, Ivar Martin, Alberto F. Morpurgo
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引用次数: 0

摘要

通过离子液体门控,场效应掺杂可以诱导少层半导体过渡金属二镓化物(TMDs)产生超导电性。虽然多年来已经收集了一些实验观测数据,但仍然缺少一个完全一致的理论图景。在这里,我们建立了一个现实的框架,将第一原理模拟的预测能力与巴丁-库珀-施里弗间隙方程的多功能性和洞察力结合起来,使这些实验合理化。与实验一致,我们发现当电子密度足够大,Q 谷被占据时,超导电性就会发生,这是电子-声子相互作用大幅增强的结果。尽管超导态是由声子驱动的,但预计它对库仑相互作用很敏感,库仑相互作用会导致谷间出现相对符号差异,从而产生 $s_{+-}$ 特性。我们定性地讨论了这种情况如何解释迄今为止尚未找到微观解释的许多观测到的物理现象,特别是大量亚隙态密度的存在,以及 T_c$ 与累积电密度的圆顶形依赖关系。我们的研究结果对半导体 TMD 中的栅极诱导超导现象进行了全面的分析,并引入了一种可能对其他多电势电子系统有价值的方法,在这些系统中,超导现象发生在相对较低的电子密度下。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Unconventional gate-induced superconductivity in transition-metal dichalcogenides
Superconductivity in few-layer semiconducting transition metal dichalcogenides (TMDs) can be induced by field-effect doping through ionic-liquid gating. While several experimental observations have been collected over the years, a fully-consistent theoretical picture is still missing. Here we develop a realistic framework that combines the predictive power of first-principles simulations with the versatility and insight of Bardeen-Cooper-Schrieffer gap equations to rationalize such experiments. The multi-valley nature of semiconducting TMDs in taken into account, together with the doping- and momentum-dependent electron-phonon and Coulomb interactions. Consistently with experiments, we find that superconductivity occurs when the electron density is large enough that the Q valleys get occupied, as a result of a large enhancement of electron-phonon interactions. Despite being phonon-driven, the superconducting state is predicted to be sensitive to Coulomb interactions, which can lead to the appearance of a relative sign difference between valleys and thus to a $s_{+-}$ character. We discuss qualitatively how such scenario may account for many of the observed physical phenomena for which no microscopic explanation has been found so far, including in particular the presence of a large subgap density of states, and the sample-dependent dome-shaped dependence of $T_c$ on accumulated electron density. Our results provide a comprehensive analysis of gate-induced superconductivity in semiconducting TMDs, and introduce an approach that will likely be valuable for other multivalley electronic systems, in which superconductivity occurs at relatively low electron density.
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