Long range Neel order in the triangular Heisenberg model

TL;DR

This paper provides strong numerical evidence for long-range Neel order in the triangular Heisenberg model, showing a gapless spectrum and quantifying the order parameter and ground state energy.

Contribution

It offers the first comprehensive quantum Monte Carlo and exact diagonalization study confirming long-range Neel order in the triangular lattice Heisenberg model.

Findings

Gapless spectrum confirmed by finite-size scaling.

Order parameter estimated at 0.41 in the thermodynamic limit.

Ground state energy per site approximately -0.5458.

Abstract

We have studied the Heisenberg model on the triangular lattice using several Quantum Monte Carlo (QMC) techniques (up to 144 sites), and exact diagonalization (ED) (up to 36 sites). By studying the spin gap as a function of the system size we have obtained a robust evidence for a gapless spectrum, confirming the existence of long range Neel order. Our best estimate is that in the thermodynamic limit the order parameter m= 0.41 +/- 0.02 is reduced by about 59% from its classical value and the ground state energy per site is e0=-0.5458 +/- 0.0001 in unit of the exchange coupling. We have identified the important ground state correlations at short distance.