Hyperfine Couplings as a Probe of Orbital Anisotropy in Heavy Fermion Materials

TL;DR

This study demonstrates that hyperfine interactions in heavy fermion materials reveal the orbital anisotropy of Ce 4f electrons, providing insights into the hybridization-driven transition from localized to itinerant electronic states.

Contribution

It introduces a method to probe orbital anisotropy via hyperfine couplings, linking it to hybridization effects in heavy fermion compounds.

Findings

Hyperfine couplings vary with transition metal in CeMIn5.

Hyperfine interactions reflect the orbital anisotropy of Ce 4f electrons.

Hybridization out of the Ce-In plane dominates the localized to itinerant transition.

Abstract

The transferred hyperfine interaction between nuclear and electron spins in an heavy fermion material depends on the hybridization between the $f$-electron orbitals and those surrounding a distant nucleus. In CeMIn$_5$ (M=Rh, Ir, Co), both the hyperfine coupling to the two indium sites as well as the crystalline electric field at the Ce are strongly dependent on the transition metal. We measure a series of CeRh$_{1-x}$Ir$_x$In$_5$ crystals and find that the hyperfine coupling reflects the orbital anisotropy of the ground state Ce 4$f$ wavefunction. These findings provide direct proof that the localized to itinerant transition is dominated by hybridization out of the Ce-In plane in this system.