Two scenarios for superconductivity in CeRh$_2$As$_2$

TL;DR

This paper classifies possible superconducting states in CeRh$_2$As$_2$, a heavy fermion material with two inequivalent Ce sites, proposing models that explain its complex phase diagram and transitions under magnetic fields.

Contribution

It introduces a classification framework for superconducting states in CeRh$_2$As$_2$ considering its sublattice structure and analyzes two key limits to match experimental phase diagrams.

Findings

Two scenarios for superconducting phases consistent with experiments.

Identification of intra- and inter-sublattice pairing mechanisms.

Explanation of magnetic field-induced phase transitions.

Abstract

CeRh$_2$As$_2$, a non-symmorphic heavy fermion material, was recently reported to host a remarkable 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 CeRh$_2$As$_2$ 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 inter-layer hopping dominated normal state. In both limits, we are able find two scenarios that generate phase diagrams in qualitative agreement with experiments: i) intra-sublattice pairing with an even-odd transition under magnetic field, and ii) inter-sublattice pairing with an odd-odd transition under magnetic field.