Cumulant approach to the low-temperature thermodynamics of many-body systems

TL;DR

This paper introduces a cumulant-based method for analyzing the low-temperature thermodynamics of many-body systems, capable of handling both strongly and weakly correlated regimes, with applications to high-temperature superconductors.

Contribution

It extends a cumulant formalism to evaluate excitation energies and thermodynamics at low temperatures, bridging zero and finite temperature analyses.

Findings

Effective in describing low-temperature thermodynamics of correlated systems

Applicable to high-temperature superconductor models

Provides a unified approach for different correlation regimes

Abstract

Current methods to describe the thermodynamic behavior of many-particle systems are often based on perturbation theory with an unperturbed system consisting of free particles. Therefore, only a few methods are able to describe both strongly and weakly correlated systems along the same lines. In this article we propose a cumulant approach which allows for the evaluation of excitation energies and is especially appropriate to account for the thermodynamics at low temperatures. The method is an extension of a cumulant formalism which was recently proposed to study statical and dynamical properties of many-body systems at zero temperature. The present approach merges into the former one for vanishing temperature. As an application we investigate the thermodynamics of the hole-doped antiferromagnetic phase in high-temperature superconductors in the framework of the anisotropic t-J model.