Spin-chirality decoupling and critical properties of a two-dimensional fully frustrated XY model

TL;DR

This study uses Monte Carlo simulations to demonstrate that in a two-dimensional fully frustrated XY model, spin and chirality order separately at different temperatures, with the chiral transition aligning with Ising universality and the spin transition differing from KT behavior.

Contribution

It provides clear evidence of spin-chirality decoupling and characterizes their distinct critical behaviors in the 2D fully frustrated XY model.

Findings

Chirality orders at T_c=0.45324(1) with Ising universality.

Spin orders at T_s=0.4418(5), with a non-Kosterlitz-Thouless universality.

Spin remains disordered at the chiral transition temperature.

Abstract

We study the ordering of the spin and the chirality in the fully frustrated XY model on a square lattice by extensive Monte Carlo simulations. Our results indicate unambiguously that the spin and the chirality exhibit separate phase transitions at two distinct temperatures, i. e. , the occurrence of the spin-chirality decoupling. The chirality exhibits a long-range order at T_c=0.45324(1) via a second-order phase transition, where the spin remains disordered with a finite correlation length \xi_s(T_c) \sim 120. The critical properties of the chiral transition determined from a finite-size scaling analysis for large enough systems of linear size L > \xi_s(T_c) are well compatible with the Ising universality. On the other hand, the spin exhibits a phase transition at a lower temperature T_s=0.4418(5) into the quasi-long-range-ordered phase. We found \eta(T_s)=0.201(1), suggesting that the universality of the spin transition is different from that of the conventional Kosterlitz-Thouless (KT) transition.