Nematic state in CeAuSb$_{2}$

TL;DR

This study reveals nematic order in CeAuSb$_{2}$ linked to a structural phase transition and explores its complex phase diagram under pressure, suggesting similarities to iron-based superconductors but without observed superconductivity.

Contribution

First demonstration of nematic order in CeAuSb$_{2}$ through thermodynamic and x-ray measurements, and analysis of its phase diagram under pressure.

Findings

Magnetic order is connected with a structural transition indicating nematicity.

Additional ordered states emerge under pressure at a multicritical point.

A phenomenological model supports a vestigial nematic phase similar to iron-based superconductors.

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.