Nematic state in CeAuSb${}_2$

Abstract

At ambient pressure and zero field, tetragonal CeAuSb${}_2$ hosts stripe antiferromagnetic order at $T_N=6.3$ K. Here we first show via bulk thermodynamic probes and x-ray diffraction measurements that this magnetic order is connected with a structural phase transition to a superstructure which likely breaks $C_4$ symmetry, thus signaling nematic order. The temperature-field-pressure phase diagram of CeAuSb${}_2$ subsequently reveals the emergence of additional ordered states under applied pressure at a multicritical point. Our phenomenological model supports the presence of a vestigial nematic phase in CeAuSb${}_2$ akin to iron-based high-temperature superconductors; however, superconductivity, if present, remains to be discovered.