Superconductivity without inversion and time-reversal symmetries

TL;DR

This paper explores minimal symmetry requirements for two-dimensional superconductivity, showing that certain symmetries like time-reversal and inversion are not necessary, expanding understanding of superconducting states.

Contribution

It identifies that mirror symmetry combined with either time-reversal or inversion symmetry can protect 2D superconductivity, providing classification and minimal models for these states.

Findings

Superconductivity can be protected without time-reversal or inversion symmetry.

Mirror symmetry combined with either time-reversal or inversion suffices.

Realistic models include transition metal dichalcogenides and Rashba systems under magnetic fields.

Abstract

The traditional symmetries that protect superconductivity are time-reversal and inversion. Here, we examine the minimal symmetries protecting superconductivity in two dimensions and find that time-reversal symmetry and inversion symmetry are not required, and having a combination of either symmetry with a mirror operation on the basal plane is sufficient. We classify superconducting states stabilized by these two symmetries, when time-reversal and inversion symmetries are not present, and provide realistic minimal models as examples. Interestingly, several experimentally realized systems, such as transition metal dichalcogenides and the two-dimensional Rashba system belong to this category, when subject to an applied magnetic field.