Refined symmetry indicators for topological superconductors in all space groups

TL;DR

This paper develops comprehensive symmetry indicators for all space groups to identify topological superconductors, including crystalline types, by relating invariants to Fermi surface properties, thus aiding the discovery of exotic phases.

Contribution

It extends the theory of symmetry indicators to all space groups for topological superconductors, providing exhaustive indicator groups and analysis methods.

Findings

Computed indicator groups for various symmetry settings.

Demonstrated diagnosis of topological phases via indicators.

Identified conditions for gapless bulk spectra.

Abstract

Topological superconductors are exotic phases of matter featuring robust surface states that could be leveraged for topological quantum computation. A useful guiding principle for the search of topological superconductors is to relate the topological invariants with the behavior of the pairing order parameter on the normal-state Fermi surfaces. The existing formulas, however, become inadequate for the prediction of the recently proposed classes of topological crystalline superconductors. In this work, we advance the theory of symmetry indicators for topological (crystalline) superconductors to cover all space groups. Our main result is the exhaustive computation of the indicator groups for superconductors under a variety of symmetry settings. We further illustrate the power of this approach by analyzing four-fold symmetric superconductors with or without inversion symmetry, and show that the indicators can diagnose topological superconductors with surface states of different dimensionalities or dictate gaplessness in the bulk excitation spectrum.