Quantum vs. Geometric Disorder in a Two-Dimensional Heisenberg Antiferromagnet

TL;DR

This study investigates how quantum and geometric disorder affect a two-dimensional Heisenberg antiferromagnet, revealing a quantum critical point influenced by impurity concentration and bilayer coupling.

Contribution

It introduces a numerical analysis of the phase diagram considering both quantum and geometric disorder, identifying a multicritical point at the percolation threshold.

Findings

Existence of a multicritical point at small bilayer coupling g_m = 0.15(3).

Ground state phase diagram as a function of impurity concentration p and coupling g.

Magnetic properties near the percolation threshold are influenced by proximity to the quantum critical point.

Abstract

We present a numerical study of the spin-1/2 bilayer Heisenberg antiferromagnet with random interlayer dimer dilution. From the temperature dependence of the uniform susceptibility and a scaling analysis of the spin correlation length we deduce the ground state phase diagram as a function of nonmagnetic impurity concentration p and bilayer coupling g. At the site percolation threshold, there exists a multicritical point at small but nonzero bilayer coupling g_m = 0.15(3). The magnetic properties of the single-layer material La_2Cu_{1-p}(Zn,Mg)_pO_4 near the percolation threshold appear to be controlled by the proximity to this new quantum critical point.