Random Frustration in two-dimensional spin-1/2 Heisenberg antiferromagnet

TL;DR

This study investigates how random ferromagnetic bonds in a 2D spin-1/2 antiferromagnet disrupt long-range order and induce spin-glass behavior, using analytical and numerical methods.

Contribution

It introduces a combined analytical and numerical analysis of disorder effects in 2D antiferromagnets, revealing critical disorder strength and spin-glass tendencies.

Findings

Long-range Néel order is destroyed above a critical ferromagnetic bond concentration.

Large fluctuations in spin-stiffness and structure factor near the critical point.

Potential emergence of a spin-glass phase at high disorder levels.

Abstract

The square lattice spin-1/2 antiferromagnet containing a dilute concentration, $\delta$, of randomly placed ferromagnetic nearest-neighbor bonds is studied at low-temperature via non-linear $\sigma$-model techniques and by exact diagonalization. We generally find that long-range N\' eel order is destroyed above a critical strength in the defective ferromagnetic exchange coupling-constant given by $|K_c|/J\sim \delta^{-1/2}$. We also observe large statistical fluctuations both in the spin-stiffness and in the antiferromagnetic structure-factor near this critical point, suggesting the onset of a spin-glass phase.