High-field ultrasonic study of quadrupole ordering and crystal symmetry breaking in CeRhIn5

We performed an ultrasonic measurement for the heavy-fermion compound ${\mathrm{CeRhIn}}₅$ to investigate the origin of the field-induced anisotropic phase in high magnetic fields. The transverse elastic constant ${C}_{\mathrm{T}}=({C}₁₁\ensuremath{-}{C}₁₂)/2$ and the ultrasonic attenuation coefficient ${\ensuremath{\alpha}}_{\mathrm{T}}$ show clear anomaly at ${B}^★=28.5\phantom{\rule{0.16em}{0ex}}\mathrm{T}$, which was discussed as the electronic nematic transition point. In addition, ${C}_{\mathrm{T}}$ exhibits acoustic de Haas-van Alphen oscillation below 28.5 T. These elastic anomalies around ${B}^★$ indicate an electric quadrupole ordering of ${O}_{{x}²\ensuremath{-}{y}²}$ accompanied by ${B}_{1\mathrm{g}}$ crystal symmetry breaking and Fermi surface reconstruction due to the quadrupole-strain coupling, which results from itinerant $4f$ electrons and the $p\text{\ensuremath{-}}f$ hybridized state.