Transitions and crossover phenomena in fully frustrated XY systems

TL;DR

This study investigates the phase transitions in fully frustrated XY systems and related models, revealing two closely spaced chiral and spin transitions with complex crossover behaviors through extensive Monte Carlo simulations.

Contribution

It provides new insights into the phase diagram and crossover phenomena of fully frustrated XY models, including the universality of preasymptotic regimes.

Findings

Two close chiral and spin transitions at T_ch > T_sp

Preasymptotic regime with universal features

Nonmonotonic approach with effective exponent nu_eff=0.8

Abstract

We study the two-dimensional fully frustrated XY (FFXY) model and two related models, a discretization of the Landau-Ginzburg-Wilson Hamiltonian for the critical modes of the FFXY model and a coupled Ising-XY model, by means of Monte Carlo simulations on square lattices L x L, L=O(10^3). We show that their phase diagram is characterized by two very close chiral and spin transitions, at T_ch > T_sp respectively, of the Ising and Kosterlitz-Thouless type. At T_ch the Ising regime sets in only after a preasymptotic regime, which appears universal to some extent. The approach is nonmonotonic for most observables, with a wide region controlled by an effective exponent nu_eff=0.8.