Unified picture of superconductivity and magnetism in CeRh$_2$As$_2$

TL;DR

This paper investigates the microscopic origins of multiple superconducting and magnetic phases in CeRh$_2$As$_2$, highlighting the role of a van Hove singularity and Fermi-surface nesting in phase competition.

Contribution

It provides a theoretical framework linking nonsymmorphic symmetry, van Hove singularity, and Fermi-surface nesting to the complex phase diagram of CeRh$_2$As$_2$.

Findings

Identification of two competing superconducting states with opposite parities.

Prediction of spin-density wave instabilities under strong Fermi-surface nesting.

Consistency with experimental phase diagram features.

Abstract

We study the micorscopic origin of the multiple superconducting and magnetic phases observed in CeRh$_2$As$_2$. We exploit the existence of a van Hove singularity enforced by the nonsymmorphic symmetry to conduct a renormalization group analysis. When Fermi-surface nesting is strong, we find two closely-competing superconducting states with opposite parities, as well as an instability towards specific spin-density wave states, consistent with key features of the phase diagram of CeRh$_2$As$_2$.