The two-dimensional quantum Heisenberg antiferromagnet: effective Hamiltonian approach to the thermodynamics

TL;DR

This study uses an effective Hamiltonian approach with the pure-quantum self-consistent harmonic approximation to analyze the thermodynamics of the 2D quantum Heisenberg antiferromagnet, comparing results with existing theories and experiments.

Contribution

It introduces an effective Hamiltonian method applied to the isotropic 2D quantum Heisenberg antiferromagnet, extending previous anisotropic models to better match experimental data.

Findings

Internal energy and specific heat match high-temperature expansion results.

Correlation functions and susceptibility agree with quantum Monte Carlo data.

The approach provides accurate thermodynamic predictions across different spin values.

Abstract

In this paper we present an extensive study of the thermodynamic properties of the two-dimensional quantum Heisenberg antiferromagnet on the square lattice; the problem is tackled by the pure-quantum self-consistent harmonic approximation, previously applied to quantum spin systems with easy-plane anisotropies, modeled to fit the peculiar features of an isotropic system. Internal energy, specific heat, correlation functions, staggered susceptibility, and correlation length are shown for different values of the spin, and compared with the available high-temperature expansion and quantum Monte Carlo results, as well as with the available experimental data.