Magnetic properties of the two-dimensional Heisenberg model on a triangular lattice

TL;DR

This paper investigates the magnetic properties of the two-dimensional Heisenberg model on a triangular lattice, revealing the absence of long-range order at zero temperature and analyzing spin correlations and excitation gaps.

Contribution

It applies Mori's projection operator technique to compute the spin Green's function, providing new insights into the excitation spectrum and correlations in this frustrated magnetic system.

Findings

Gaps in the spin excitation spectrum at classical Neel wave vectors

Absence of antiferromagnetic long-range order at T=0

Good agreement of spin correlations with exact diagonalization

Abstract

The spin Green's function of the antiferromagnetic Heisenberg model on a triangular lattice is calculated using Mori's projection operator technique. At T=0 the spin excitation spectrum is shown to have gaps at the wave vectors of the classical Neel ordering. This points to the absence of the antiferromagnetic long-range order in the ground state. The calculated spin correlation on the neighboring sites of the same sublattice is in good agreement with the value derived from exact diagonalization. The temperature dependencies of the spin correlations and the gaps are calculated.