Thermodynamics of the quantum easy-plane antiferromagnet on the triangular lattice

TL;DR

This paper investigates the thermodynamic properties of the quantum easy-plane antiferromagnet on a triangular lattice, revealing how quantum effects influence transition temperatures and thermodynamic quantities across different spin values.

Contribution

It introduces a method to evaluate quantum effects on thermodynamics of the XXZ triangular-lattice antiferromagnet using PQSCHA combined with classical MC simulations.

Findings

Quantum transition temperatures decrease with smaller spin values.

Internal energy, specific heat, and correlation length are computed for various spins.

Quantum effects lower the transition temperatures compared to classical predictions.

Abstract

The classical XXZ triangular-lattice antiferromagnet (TAF) shows both an Ising and a BKT transition, related to the chirality and the in-plane spin components, respectively. In this paper the quantum effects on the thermodynamic quantities are evaluated by means of the pure-quantum self-consistent harmonic approximation (PQSCHA), that allows one to deal with any spin value through classical MC simulations. We report the internal energy, the specific heat, and the in-plane correlation length of the quantum XX0 TAF, for S=1/2, 1, 5/2. The quantum transition temperatures turn out to be smaller the smaller the spin, and agree with the few available theoretical and numerical estimates.