Nematostriction in frustrated two-dimensional Heisenberg models

TL;DR

This paper explores how magnetoelastic couplings influence nematic phase transitions in frustrated 2D Heisenberg models, revealing shifts in transition order and phonon spectrum modifications.

Contribution

It introduces a diagrammatic self-consistent Nematic Bond Theory to analyze magnetoelastic effects on nematic transitions in square and triangular lattices.

Findings

On the square lattice, the transition shifts from continuous to weakly first-order with increasing magnetoelastic coupling.

On the triangular lattice, the transition remains discontinuous regardless of coupling strength.

Magnetoelastic feedback significantly alters the critical temperature and phonon spectrum.

Abstract

We investigate the nematic phase transition in the Heisenberg $J_1$-$J_2$-model on square and triangular lattices, accounting for finite lattice compressibility and bond-length-dependent magnetic exchange. Using Nematic Bond Theory, a diagrammatic self-consistent method, we study the nematostriction that happens when the onset of nematic order in the spin-system drives a concomitant structural phase transition. We analyze the mechanisms by which the magnetoelastic couplings renormalize the critical temperature and modify the phonon spectrum. The magnetoelastic feeback can also alter fundamentally the nature of the phase transition. Specifically, on the square lattice, the transition shifts from continuous to weakly first-order (discontinuous) beyond a critical magnetoelastic coupling threshold. Conversely, on the triangular lattice, the transition remains discontinuous regardless of coupling strength.