Dynamical mean-field theory for dense spin systems at finite temperature

TL;DR

This paper extends the spinDMFT method to finite temperatures, enabling the calculation of thermodynamic properties and imaginary-time correlations in dense spin systems.

Contribution

The work develops a finite-temperature extension of spinDMFT, allowing for broader analysis of spin dynamics and thermodynamics beyond infinite temperature.

Findings

Good agreement with finite-size system correlations in random-coupling systems

Accurate results for ferromagnetic systems

Large discrepancies observed in antiferromagnetic systems

Abstract

In recent years, a method for computing spin dynamics at infinite temperature (spinDMFT) was developed. It utilizes the ideas of dynamical mean-field theory for fermions: single-site approximation and a self-consistency condition to approximate time-dependent spin correlations. In this work, we develop a crucial extension of the method to systems at finite temperature, able to compute imaginary-time correlations and thermodynamical quantities. We benchmark the method by comparison to results in finite-size systems, obtaining very good agreement with correlations in a random-coupling system, good agreement for a ferromagnetic system and large discrepancies in the case of an antiferromagnet. We note the appearance of ferromagnetic order in the method. We discuss possible extensions and potential applications of the approach.