Thermodynamical Properties of a Spin 1/2 Heisenberg Chain Coupled to Phonons

TL;DR

This paper uses quantum Monte Carlo simulations to analyze the thermodynamic properties of a one-dimensional spin-1/2 Heisenberg chain coupled to phonons, revealing phase transitions and dimerization effects.

Contribution

It introduces a method capable of handling up to 100 phonons per site with minimal truncation errors, providing detailed insights into spin-phonon coupled systems.

Findings

Evidence of a transition from a gapless to a massive phase.

Dimerization proportional to g^2/Ω for T<2J.

Accurate calculation of susceptibility, specific heat, and phonon occupation.

Abstract

We performed a finite-temperature quantum Monte Carlo simulation of the one-dimensional spin-1/2 Heisenberg model with nearest-neighbor interaction coupled to Einstein phonons. Our method allows to treat easily up to 100 phonons per site and the results presented are practically free from truncation errors. We studied in detail the magnetic susceptibility, the specific heat, the phonon occupation, the dimerization, and the spin-correlation function for various spin-phonon couplings and phonon frequencies. In particular we give evidence for the transition from a gapless to a massive phase by studying the finite-size behavior of the susceptibility. We also show that the dimerization is proportional to $g^2/\Omega$ for $T<2J$.