Field-induced transition from even to odd parity superconductivity in CeRh$_2$As$_2$

TL;DR

This study uncovers a field-induced transition between even and odd parity unconventional superconducting phases in CeRh$_2$As$_2$, driven by local inversion-symmetry breaking and Rashba spin-orbit coupling, with high critical fields.

Contribution

It reveals a novel transition between even and odd parity superconducting states in CeRh$_2$As$_2$ induced by magnetic field, highlighting the role of local inversion symmetry breaking.

Findings

High-field superconducting phase has a critical field of 14 T.

Transition between two superconducting phases driven by c-axis magnetic field.

Local inversion symmetry breaking enables Rashba spin-orbit coupling to influence superconductivity.

Abstract

We report the discovery of two-phase unconventional superconductivity in CeRh$_2$As$_2$. Using thermodynamic probes, we establish that the superconducting critical field of its high-field phase is as high as 14 T, remarkable in a material whose transition temperature is 0.26 K. Furthermore, a $c$-axis field drives a transition between two different superconducting phases. In spite of the fact that CeRh$_2$As$_2$ is globally centrosymmetric, we show that local inversion-symmetry breaking at the Ce sites enables Rashba spin-orbit coupling to play a key role in the underlying physics. More detailed analysis identifies the transition from the low- to high-field states to be associated with one between states of even and odd parity.