Enhanced hybridization sets the stage for electronic nematicity in CeRhIn5

Abstract

High magnetic fields induce a pronounced in-plane electronic anisotropy in the tetragonal antiferromagnetic metal CeRhIn${}_5$ at $H^{\ast }\gtrsim 30$ T for fields $\simeq 20^{\mathrm{o}}$ off the $c$-axis. Here we investigate the response of the underlying crystal lattice in magnetic fields to $45$ T via high-resolution dilatometry. Within the antiferromagnetic phase of CeRhIn${}_5$, a finite magnetic field component in the tetragonal $ab$-plane explicitly breaks the tetragonal ($C_4$) symmetry of the lattice well below $H^{\ast }$ revealing a finite nematic susceptibility at low fields. A modest magnetostriction anomaly, $dL/L=-1.8\times 10^{-6}$, at $H^{\ast }=31$ T hence presumably marks the crossover to a fluctuating nematic phase with large electronic nematic susceptibility. Magnetostriction quantum oscillations confirm a Fermi surface change at $H^{\ast }$ with the emergence of new orbits. By analyzing the field-induced change in the crystal-field ground state, we conclude that the in-plane Ce $4f$ hybridization is enhanced at $H^{\ast }$, carrying the in-plane $f$-electron anisotropy to the Fermi surface. We argue that the nematic behavior observed in this prototypical heavy-fermion material is of electronic origin, and is driven by the hybridization between $4f$ and conduction electrons.