Topological crystalline superconductivity in locally noncentrosymmetric CeRh₂As₂

Abstract

Recent discovery of superconductivity in CeRh₂As₂ clarified an unusual H−T phase diagram with two superconducting phases [Khim et al. Science, 373, 1012 (2021)]. The experimental observation has been interpreted based on the even-odd parity transition characteristic of locally noncentrosymmetric superconductors. Indeed, inversion symmetry is locally broken at the Ce site, and CeRh₂As₂ molds a class of exotic superconductors. The low-temperature and high-field superconducting phase is a candidate for the odd-parity pair-density-wave state, suggesting a possibility of topological superconductivity like spin-triplet superconductors. In this Letter, we first derive the formula expressing the ℤ₂ invariant of glide symmetric and time-reversal symmetry-broken superconductors by the number of Fermi surfaces on a glide invariant line. Next, we conduct first-principles calculations for the electronic structure of CeRh₂As₂. Combining the results, we show that the field-induced odd-parity superconducting phase of CeRh₂As₂ is a platform of topological crystalline superconductivity protected by nonsymmorphic glide symmetry and accompanied by boundary Majorana fermions.