Unveiling Magnetic Frustration via the Elastocaloric Effect

TL;DR

This paper investigates how uniaxial strain affects frustrated magnetic systems, revealing that the elastic Grüneisen ratio signals maximal frustration and phase transitions, with implications for experimental detection of quantum phases.

Contribution

It provides a theoretical analysis of the thermodynamic response of frustrated magnets to strain, highlighting the universal behavior of the elastic Grüneisen ratio near frustration points.

Findings

The elastic Grüneisen ratio diverges at low temperature near maximal frustration.

Strain tuning can induce and probe spin-liquid phases in Ising models.

Multiple zero-temperature phase transitions are identified in the Heisenberg model.

Abstract

Motivated by experimental progress in pressure and strain tuning of quantum materials, we examine the thermodynamic response of frustrated magnets to uniaxial strain. Specifically, we study Ising and Heisenberg models on spatially anisotropic triangular (and, for the Ising model, also kagome) lattices. We determine the entropy as a function of temperature and strain, and use it to compute the elastic Gr\"uneisen ratio $\eta$. The Ising models can be strain-tuned into and out of classical spin-liquid phases, and we show that $\eta$ can become arbitrarily large at low temperature $T$ near the point of maximal frustration, a universal hallmark of an extensive ground-state entropy. In contrast, the spin-$1/2$ Heisenberg model is moderately frustrated and displays multiple $T=0$ phase transitions. These transitions dominate $\eta$ at low $T$ while the intermediate-$T$ behavior is similar to that of the Ising model. We discuss the extent to which the elastic Gr\"uneisen ratio can be used to deduce the phase diagram, and we connect our results to recent experiments on triangular-lattice magnets.