Universal features of nonequilibrium Ising models in contact with two thermal reservoirs

TL;DR

This paper investigates universal properties of nonequilibrium phase transitions in all-to-all Ising models coupled with two thermal reservoirs, revealing how external parameters influence the nature of phase transitions.

Contribution

It provides a comprehensive analysis of how different external parameters affect phase transition types in nonequilibrium Ising models with two thermal baths.

Findings

Presence of continuous, discontinuous, and tricritical points under symmetric external parameters.

Absence of tricriticality under antisymmetric external parameters, leading to only critical or discontinuous transitions.

Probability distribution becomes Boltzmann-Gibbs-like when switching between reservoirs is fast, regardless of model parameters.

Abstract

We derive generic properties of nonequilibrium phase transitions in all-to-all Ising models placed in contact with two thermal reservoirs, in which parameters (temperatures, interactions and field parameters) assume arbitrary values depending on the contact with each thermal bath. The presence of different kinds of external parameters leads to remarkably different sort of phase transitions. While continuous, discontinuous and even tricritical points are presented when external parameters are symmetric (e.g. the case of energetic barriers or different couplings between the system and thermal baths), the tricriticality is absent when external parameters are antisymmetric (e.g. the case of magnetic fields or biased drivings) implying that solely critical or discontinuous are possible. In such latter case, the probability distribution acquires the Boltzmann-Gibbs like form, irrespectively the model parameters when the switching between thermal reservoirs is sufficiently fast. Our work sheds light about the differences between equilibrium and nonequilibrium ingredients and theirs consequences upon phase transitions.