Two scenarios for superconductivity in CeRh2As2

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. In this work, 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 identified two scenarios for the superconducting phases observed in CeRh₂As₂: (i) intrasublattice pairing with an even-odd transition under z-axis magnetic field, associated with the previously proposed PDW scenario, and (ii) intersublattice pairing with an odd-odd transition under z-axis magnetic field, as a new pair or order parameter candidates. Our work stimulates more efforts in the field of complex locally noncentrosymmetric materials with extra internal degrees of freedom.