Elastic Quantum Criticality in Nematics and Altermagnets via the Elasto-Caloric Effect

TL;DR

This paper investigates how the elastocaloric effect reveals non-Fermi-liquid behavior near quantum critical points in nematic and altermagnetic systems, highlighting its potential as a sensitive probe for elastic quantum criticality.

Contribution

It demonstrates that the elastocaloric effect remains a dominant non-Fermi-liquid indicator near quantum critical points, even with lattice coupling, and extends this understanding to altermagnetic systems.

Findings

Elastocaloric effect deviates from expected Fermi-liquid behavior near QCPs.

Lattice coupling weakens but does not eliminate non-Fermi-liquid signatures in ECE.

Similar ECE responses are predicted for altermagnetic quantum critical points.

Abstract

The coupling between electronic nematic degrees of freedom and acoustic phonons is known to significantly alter the universality class of a nematic quantum critical point (QCP). While non-Fermi-liquid behaviour emerges in the absence of lattice coupling, the inclusion of interactions with acoustic phonons results in observables such as heat capacity and single-particle scattering rate exhibiting only subleading non-analytic corrections to dominant Fermi-liquid terms. In this work, we demonstrate that the elastocaloric effect (ECE) -- the adiabatic temperature change under varying strain -- and the thermal expansion deviate from this pattern. Despite lattice coupling weakening the singularity of the ECE, it preserves a dominant non-Fermi-liquid temperature dependence. By drawing analogies between nematic systems and field-tuned altermagnets, we further show that similar responses are expected for the ECE near altermagnetic QCPs. We classify the types of piezomagnetic couplings and analyse the regimes arising from field-tuned magnetoelastic interactions. Our findings are shown to be consistent with the scaling theory for elastic quantum criticality and they further emphasize the suitability of the ECE as a sensitive probe near QCPs.