Quantum disordered ground state for the frustrated square lattice

TL;DR

This paper uses Quantum Monte Carlo simulations to explore the phase diagram of an anisotropic spin-1/2 Heisenberg model on a square lattice, revealing a quantum disordered ground state between classical magnetic phases.

Contribution

It provides the first detailed phase diagram showing a quantum disordered phase in the frustrated square lattice Heisenberg model.

Findings

Identification of classical magnetic phases for dominant interactions

Detection of a quantum disordered region with no long-range order

Evidence of long-ranged dimer correlations in the disordered phase

Abstract

We present Quantum Monte-Carlo simulations of an exchange-anisotropic spin-1/2 Heisenberg model on a square lattice with nearest and next-nearest neighbor interactions. The ground state phase diagram shows two classical magnetically ordered phases for dominating antiferromagnetic S^z-interactions and for large quantum fluctuations a ferromagnetic order in the x-y plane. In between a finite region is detected where neither classical nor quantum mechanical order, e.g. long-ranged dimer correlations, are found.