Quantum-Critical Behavior in a Two-Layer Antiferromagnet

TL;DR

This paper investigates quantum critical behavior in a two-layer antiferromagnet using quantum Monte Carlo simulations, confirming theoretical predictions and resolving previous discrepancies with the sigma model.

Contribution

It provides numerical evidence of quantum criticality in a two-layer antiferromagnet and reconciles earlier differences with $O(N)$ sigma model predictions.

Findings

Quantum critical behavior observed at low temperatures.

Good agreement with $1/N$ calculations for the sigma model.

Resolution of previous discrepancies in critical properties.

Abstract

We analyze quantum Monte Carlo data in the vicinity of the quantum transition between a Neel state and a quantum paramagnet in a two-layer, square lattice spin 1/2 Heisenberg antiferromagnet. The real-space correlation function and the universal amplitude ratio of the structure factor and the dynamic susceptibility show clear evidence of quantum critical behavior at low temperatures. The numerical results are in good quantitative agreement with $1/N$ calculations for the $O(N)$ non-linear sigma model. A discrepancy, reported earlier, between the critical properties of the antiferromagnet and the sigma model is resolved. We also discuss the values of prefactors of the dynamic susceptibility and the structure factor in a single layer antiferromagnet at low $T$.