Direct Calculation of Thermodynamic Quantities for Heisenberg Model

TL;DR

This paper presents a direct calculation method for thermodynamic quantities of the Heisenberg model at finite temperature, avoiding traditional complex techniques and providing explicit cluster expansion coefficients.

Contribution

It introduces a novel direct calculation approach for the Heisenberg model's thermodynamics, including explicit cluster expansion coefficients, aligning with established methods.

Findings

Derived free energy without Thermal Bethe Ansatz

Explicit cluster expansion coefficients provided

Results agree with traditional methods

Abstract

The XXX Heisenberg model is studied at finite temperature. The free energy is derived without recourse to Thermal Bethe Ansatz method and Quantum Transfer Matrix method. The result perfectly agrees with the free energy derived by Thermal Bethe Ansatz method. An explicit expression of the cluster expansion coefficient in arbitrary order is presented for the first time.