Uniformly frustrated XY model without vortex-pattern ordering

TL;DR

This paper investigates the frustrated XY model on a dice lattice, revealing extensive ground state degeneracy and a phase transition associated with half-vortex pair dissociation, without vortex-pattern ordering.

Contribution

It demonstrates that the frustrated XY model exhibits high ground state degeneracy and a finite-temperature phase transition driven by half-vortex dissociation, without selecting a specific vortex pattern.

Findings

Ground state degeneracy prevents vortex pattern stabilization.

Finite helicity modulus at low temperatures indicates phase rigidity.

Phase transition involves dissociation of half-vortex pairs.

Abstract

The uniformly frustrated XY model with f=1/3 on a dice lattice is shown to possess a so well developed accidental degeneracy of its ground states that the difference between the free energies of fluctuations does not lead to the stabilization of a particular vortex pattern down to zero temperature. Nonetheless, at low temperatures the system is characterized by a finite helicity modulus whose vanishing (at a finite temperature) is related with the dissociation of half-vortex pairs.