Superconductivity and Local Inversion-Symmetry Breaking

Abstract

Inversion and time reversal are essential symmetries for the structure of Cooper pairs in superconductors. The loss of one or both leads to modifications to this structure and can change the properties of the superconducting phases in profound ways. Lacking inversion, superconductivity in noncentrosymmetric materials has become an important topic, in particular, in the context of topological superconductivity as well as unusual magnetic and magneto-electric properties. Recently, crystal structures with local, but not global inversion-symmetry breaking have attracted attention, as superconductivity can exhibit phenomena not naively expected in centrosymmetric materials. After introducing the concept of locally noncentrosymmetric crystals and different material realizations, we discuss consequences of such local symmetry breaking on the classification, the expected and, in parts, already observed phenomenology of unconventional superconductivity, and possible topological superconducting phases.

Quantum-geometry-induced anapole superconductivity

“…Many exotic superconductors of recent interest have multiple sublattices which do not lie on the inversion center. UTe 2 13 and CeRh 2 As 2 67 are examples of such locally noncentrosymmetric superconductors, and a part of materials is listed in a review article 68 . Before demonstrating the quantum-geometryinduced anapole superconductivity in UTe 2 , we show that the locally noncentrosymmetric superconductors are generically the platform of anapole superconductivity and clarify the conditions for it.…”

Diversified Ruderman-Kittel-Kasuya-Yosida Interactions in a Nonsymmorphic Crystal

“…Correspondingly, the DM magnetic interaction can be expected in such systems. Moreover, besides magnetism it has been demonstrated that the local inversionsymmetry-breaking effect may be essential in the odd-parity superconductivity [46][47][48] and the topological superconductivity [41,49].…”