Order-Disorder Transition in a Two-Layer Quantum Antiferromagnet

TL;DR

This paper investigates the quantum phase transition from order to disorder in a two-layer antiferromagnetic system, identifying the critical coupling ratio and analyzing its critical behavior and finite-temperature properties.

Contribution

It provides the critical inter-plane coupling ratio for the transition and confirms the universality class, also comparing finite-temperature results with theoretical models.

Findings

Critical ratio J_c = 2.51 ± 0.02 for the phase transition

Critical behavior aligns with 3D classical Heisenberg universality

Susceptibility shows quantum critical behavior at high temperatures

Abstract

We have studied the antiferromagnetic order -- disorder transition occurring at $T=0$ in a 2-layer quantum Heisenberg antiferromagnet as the inter-plane coupling is increased. Quantum Monte Carlo results for the staggered structure factor in combination with finite-size scaling theory give the critical ratio $J_c = 2.51 \pm 0.02$ between the inter-plane and in-plane coupling constants. The critical behavior is consistent with the 3D classical Heisenberg universality class. Results for the uniform magnetic susceptibility and the correlation length at finite temperature are compared with recent predictions for the 2+1-dimensional nonlinear $\sigma$-model. The susceptibility is found to exhibit quantum critical behavior at temperatures significantly higher than the correlation length.