Two scenarios for superconductivity in CeRh2As2

Abstract

CeRh2As2, a nonsymmorphic heavy fermion material, was recently reported to host a remarkable temperature versus z-axis magnetic-field phase diagram with two superconducting phases. In this material, the two inequivalent Ce sites per unit cell, related by inversion symmetry, introduce a sublattice structure corresponding to an extra internal degree of freedom. Here we propose a classification of the possible superconducting states in CeRh2As2 from the two Ce-sites' perspective. Based on the superconducting fitness analysis and the quasiclassical Eilenberger equations, we discuss two limits: Rashba spin-orbit coupling and interlayer hopping dominated normal state. In both limits, we are able to find two scenarios that generate phase diagrams in qualitative agreement with experiments: (i) intrasublattice pairing with an even-odd transition under z-axis magnetic field and (ii) intersublattice pairing with an odd-odd transition under z-axis magnetic field.