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

We performed an ultrasonic measurement for the heavy-fermion compound CeRhIn5 to investigate the origin of the field-induced anisotropic phase in high magnetic fields. The transverse elastic constant CT=(C11-C12)/2 and the ultrasonic attenuation coefficient αT show clear anomaly at B∗=28.5T, which was discussed as the electronic nematic transition point. In addition, CT exhibits acoustic de Haas-van Alphen oscillation below 28.5 T. These elastic anomalies around B∗ indicate an electric quadrupole ordering of Ox2-y2 accompanied by B1g crystal symmetry breaking and Fermi surface reconstruction due to the quadrupole-strain coupling, which results from itinerant 4f electrons and the p-f hybridized state.