Semiclassical approach to the thermodynamics of spin chains

TL;DR

This paper applies a semiclassical PQSCHA method combined with Fisher's exact solution to efficiently evaluate thermodynamic properties of 1D Heisenberg spin chains, revealing the significance of topological effects mainly at low spins and temperatures.

Contribution

It introduces a semiclassical approach that simplifies thermodynamic calculations of spin chains, integrating classical-like methods with exact solutions for improved accuracy.

Findings

Good agreement with Monte Carlo simulations for S>1 antiferromagnets

Topological effects are significant mainly for low spin values and temperatures

The method provides an almost fully analytical evaluation of thermodynamic quantities

Abstract

Using the PQSCHA semiclassical method, we evaluate thermodynamic quantities of one-dimensional Heisenberg ferro- and antiferromagnets. Since the PQSCHA reduces their evaluation to classical-like calculations, we take advantage of Fisher's exact solution to get all results in an almost fully analytical way. Explicitly considered here are the specific heat, the correlations length and susceptibility. Good agreement with Monte Carlo simulations is found for S>1 antiferromagnets, showing that the relevance of the topological terms and of the Haldane gap is significant only for the lowest spin values and temperatures.