Theory of (s+id) pairing in mixed-valent correlated metals
Theory of (s+id) pairing in mixed-valent correlated metals
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DOI：
10.1103/physrevb.102.214509
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发表时间：
2020-07
影响因子：
3.7
通讯作者：
E. Nica;O. Erten
中科院分区：
文献类型：
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作者：
E. Nica;O. Erten
最近发现的超导电性在方形平面镍酸盐以及长期困惑的实验在重费米子超导体的动机，我们研究库珀配对相关的d$-电子耦合到一个带的弱相关电子。我们进行自洽的大N计算的一个有效的$t-J$模型的$d$-电子与额外的杂交。与以往的研究不同的混合价系统，我们专注于参数制度，其中两个杂化带是相关的，以确定配对对称性。对于足够强的杂交，我们发现一个强大的$s+id$配对，打破时间反演和点群对称的混合价制度。我们的结果说明了如何本质上多带系统，如重费米子可以支持一些高度非平凡的配对状态。它们还提供了一个假定的微观实现以前的唯象建议的$s+id$配对，并提出了一个潜在的解决方案，令人困惑的实验中的重费米子超导体，如U${1-x}$Th$_x$Be$_{13}$，表现出两个超导相变和一个完整的间隙在较低的温度。
Motivated by the recent discovery of superconductivity in square-planar nickelates as well as by longstanding puzzling experiments in heavy-fermion superconductors, we study Cooper pairing between correlated $d$-electrons coupled to a band of weakly-correlated electrons. We perform self-consistent large N calculations on an effective $t-J$ model for the $d$-electrons with additional hybridization. Unlike previous studies of mixed-valent systems, we focus on parameter regimes where both hybridized bands are relevant to determining the pairing symmetry. For sufficiently strong hybridization, we find a robust $s+id$ pairing which breaks time-reversal and point-group symmetries in the mixed-valent regime. Our results illustrate how intrinsically multi-band systems such as heavy-fermions can support a number of highly non-trivial pairing states. They also provide a putative microscopic realization of previous phenomenological proposals of $s+id$ pairing and suggest a potential resolution to puzzling experiments in heavy-fermion superconductors such as U$_{1-x}$Th$_x$Be$_{13}$ which exhibit two superconducting phase transitions and a full gap at lower temperatures.