Band dependent inter-layer $f$-electron hybridization in CeRhIn$_5$

TL;DR

This study uses resonant ARPES with polarized light to analyze the band-dependent hybridization of 4f electrons in CeRhIn$_5$, revealing how subtle electronic interactions influence its ground state and transition between antiferromagnetism and superconductivity.

Contribution

It provides detailed experimental insights into the 4f crystal field states and hybridization mechanisms in CeRhIn$_5$, highlighting band-dependent hybridization effects that were previously not well understood.

Findings

Identification of two Ce 4f crystal-electric-field levels.

Observation of weakly dispersive Kondo resonances.

Evidence of band-dependent hybridization primarily involving Ce 4f and Rh/In orbitals.

Abstract

A key issue in heavy fermion research is how subtle changes in the hybridization between the 4$f$ (5$f$) and conduction electrons can result in fundamentally different ground states. CeRhIn$_5$ stands out as a particularly notable example: replacing Rh by either Co or Ir, located above or below Rh in the periodic table, antiferromagnetism gives way to superconductivity. In this photoemission study of CeRhIn$_5$, we demonstrate that the use of resonant ARPES with polarized light allows to extract detailed information on the 4$f$ crystal field states and details on the 4$f$ and conduction electron hybridization which together determine the ground state. We directly observe weakly dispersive Kondo resonances of $f$-electrons and identify two of the three Ce $4f_{5/2}^{1}$ crystal-electric-field levels and band-dependent hybridization, which signals that the hybridization occurs primarily between the Ce $4f$ states in the CeIn$_3$ layer and two more three-dimensional bands composed of the Rh $4d$ and In $5p$ orbitals in the RhIn$_2$ layer. Our results allow to connect the properties observed at elevated temperatures with the unusual low-temperature properties of this enigmatic heavy fermion compound.