Nematic order, which is characterized by rotational symmetry breaking, and its corresponding fluctuations, may play crucial roles in the phase diagrams of high Tc superconductors. In particular, it has been suggested that the nematic quantum critical fluctuations arising from a putative quantum critical point (QCP) in the phase diagrams of iron-based superconductors like BaFe2As2 provide the superconducting pairing mechanism. The precise nature of nematic QCPs remains a mystery, as superconducting domes seem to nearly universally emerge in their proximity and disguise their inherent thermodynamic and transport properties. Intermetallic materials containing 4f electrons provide an exciting alternative to uncovering “bare” nematic QCPs, as local quadrupoles can align in a ferroquadrupolar phase transition that spontaneously breaks the rotational symmetry of the lattice while preserving translational symmetry, thereby realizing “locally driven” nematicity. The low energy scales of these transitions imply they can be experimentally suppressed to 0K, enabling the study of putative nematic QCPs. I will present two such examples, the rare-earth intermetallics TmAg2 and YbRu2Ge2, and show results of probing them with recently developed strain-based probes elastoresistivity and the elastocaloric effect. These experimental techniques measure the nematic susceptibility of the material, and I will discuss the implications of these measurements performed in the proximity of magnetic field tuned nematic QCPs. Specifically the elastocaloric effect is a powerful method of probing the entropy of these systems, and I will briefly show other exotic strain-tunable phases for which this quantity elucidates the nature of their susceptibilities and order parameters as well.
Dr. Elliott Rosenberg received his Ph.D in experimental condensed matter physics working under Prof. Ian Fisher at Stanford University. His work concentrated on developing and applying novel strain-based measurements to study rotational symmetry breaking in rare-earth intermetallics. He has gone on to work as a postdoctoral scholar at the University of Washington to expand his expertise in crystal growth and strain techniques. There, he has addressed questions in the field related to the symmetry nature of numerous exotic phases, ranging from unconventional kagome superconductors to three-state nematic systems. He hopes to continue to push the frontier of strain measurements to probe higher-order symmetry phases which combine electronic correlations with topology as a leader of his future lab.