Power-law correlated phase in random-field XY models and randomly pinned charge-density waves

TL;DR

This study uses Monte Carlo simulations to explore phase transitions in a random-field XY model with a specific disorder pattern, revealing a power-law correlated phase with unique decay properties.

Contribution

It demonstrates the existence of a power-law correlated phase in a disordered XY model and characterizes its critical properties through detailed simulations.

Findings

Identification of a power-law correlated phase with |k|^{-3} decay

Divergence of magnetic susceptibility at phase transition

Approximate |k|^{-2.87} decay near criticality

Abstract

Monte Carlo simulations have been used to study the Z6 ferromagnet in a random field on simple cubic lattices, which is a simple model for randomly pinned charge-density waves. The random field is chosen to have infinite strength on a fraction x of the sites of the lattice, and to be zero on the remaining sites. For x= 1/16 there are two phase transitions. At low temperature there is a ferromagnetic phase, which is stabilized by the six-fold nonrandom anisotropy. The intermediate temperature phase is characterized by a |k|^(-3) decay of two-spin correlations, but no true ferromagnetic order. At the transition between the power-law correlated phase and the paramagnetic phase the magnetic susceptibility diverges, and the two-spin correlations decay approximately as |k|^(-2.87).