First-order and Berezinskii-Kosterlitz-Thouless phase transitions in two-dimensional generalized XY models

TL;DR

This paper investigates phase transitions in generalized 2D XY models, revealing the existence of first-order and Berezinskii-Kosterlitz-Thouless transitions, and characterizing three distinct regions with critical parameters and mechanisms.

Contribution

It demonstrates that generalized XY models can exhibit both first-order and BKT phase transitions, identifying critical parameters and underlying mechanisms.

Findings

Identification of the critical parameter q for phase transition

Existence of three distinct regions with different transition types

Estimation of critical temperatures for transitions

Abstract

The aim of this paper is to illustrate that generalized two-dimensional XY models (proposed by Romano and Zagrebnov) may also support a first-order phase transition. Two approaches are employed to accurately determine the critical parameter $q$ at which such a transition takes place. Furthermore, we show that the model is characterized by three distinct regions concerning both first-order and Berezinskii-Kosterlitz-Thouless phase transitions. Finally, the underlying mechanisms governing such transitions are presented, along with an estimation of the critical temperatures.