Variational wave functions for the spin-Peierls transition in the Su-Schrieffer-Heeger model with quantum phonons

TL;DR

This paper develops a variational wave function approach to study the ground state of the spin-phonon coupled Su-Schrieffer-Heeger model, accurately capturing the spin-Peierls transition and applicable to various regimes and dimensions.

Contribution

It introduces a versatile variational Ansatz that treats spins and phonons equally, enabling accurate analysis of the spin-Peierls transition beyond previous methods.

Findings

Good agreement with density-matrix renormalization group results in 1D

Accurately describes the spin-Peierls transition

Applicable to higher dimensions and broader regimes

Abstract

We introduce variational wave functions to evaluate the ground-state properties of spin-phonon coupled systems described by the Su-Schrieffer-Heeger model. Quantum spins and phonons are treated on equal footing within a Monte Carlo sampling, and different regimes are investigated. We show that the proposed variational Ansatz yields good agreement with previous density-matrix renormalization group results in one dimension and is able to accurately describe the spin-Peierls transition. This variational approach is neither constrained by the magnetoelastic-coupling strength nor by the dimensionality of the systems considered, thus allowing future investigations in more general cases, which are relevant to spin-liquid and topological phases in two spatial dimensions.