Spectroscopic evidence of Kondo-induced quasi-quartet in CeRh$_2$As$_2$

TL;DR

This study uses x-ray spectroscopy to demonstrate the formation of a Kondo-induced quasi-quartet ground state in the heavy fermion superconductor CeRh$_2$As$_2$, revealing complex orbital coupling and hybridization effects.

Contribution

It provides direct spectroscopic evidence for a Kondo-driven quasi-quartet crystal-field ground state in CeRh$_2$As$_2$, advancing understanding of its electronic structure.

Findings

Confirmation of Kondo hybridization via core-level photoelectron and x-ray absorption spectroscopy.

Identification of the $| ext{Gamma}_7^- angle$ state as dominant in the ground state.

Observation of temperature-dependent dichroism indicating Kondo physics influence.

Abstract

CeRh$_2$As$_2$ is a new multiphase superconductor with strong suggestions for an additional itinerant multipolar ordered phase. The modeling of the low temperature properties of this heavy fermion compound requires a quartet Ce$^{3+}$ crystal-field ground state. Here we provide the evidence for the formation of such a quartet state using x-ray spectroscopy. Core-level photoelectron and x-ray absorption spectroscopy confirm the presence of Kondo hybridization in CeRh$_2$As$_2$. The temperature dependence of the linear dichroism unambiguously reveils the impact of Kondo physics for coupling the Kramer's doublets into an effective quasi-quartet. Non-resonant inelastic x-ray scattering data find that the $|\Gamma_7^- \rangle$ state with its lobes along the 110 direction of the tetragonal structure ($xy$ orientation) contributes most to the multi-orbital ground state of CeRh$_2$As$_2$.