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

Abstract

We uncover universal features of nonequilibrium phase transitions in all-to-all Ising models coupled to two thermal reservoirs with arbitrary temperatures, interactions, and external drivings. We show that the symmetry of external parameters fundamentally controls the nature of phase transitions: symmetric drivings allow for continuous, discontinuous, and tricritical behavior, whereas antisymmetric drivings suppress the tricriticality, yielding only critical or discontinuous transitions. Remarkably, in the latter case and in the fast-switching limit, the nonequilibrium stationary distribution acquires a Boltzmann-Gibbs–like form irrespective of the model details. Our work sheds light on the differences between equilibrium and nonequilibrium ingredients and genuinely nonequilibrium features in collective phase transitions.