Phase diagram and specific heat of a nonequilibrium Curie-Weiss model

TL;DR

This paper investigates how nonequilibrium driving, via rapid temperature switching, alters the phase diagram and specific heat behavior of a Curie-Weiss model, revealing new phases and divergence phenomena.

Contribution

It introduces a nonequilibrium Curie-Weiss model with a rapidly switching thermal bath, showing modified phase stability and novel specific heat behavior near phase transitions.

Findings

Critical temperature shifts with nonequilibrium driving

Paramagnetic phase stability expands at low temperatures

Specific heat diverges at the critical point under nonequilibrium conditions

Abstract

Adding activity or driving to a thermal system may modify its phase diagram and response functions. We study that effect for a Curie-Weiss model where the thermal bath switches rapidly between two temperatures. The critical temperature moves with the nonequilibrium driving, opening up a new region of stability for the paramagnetic phase (zero magnetization) at low temperatures. Furthermore, phase coexistence between the paramagnetic and ferromagnetic phases becomes possible at low temperatures. Following the excess heat formalism, we calculate the nonequilibrium thermal response and study its behaviour near phase transitions. Where the specific heat at the critical point makes a finite jump in equilibrium (discontinuity), it diverges once we add the second thermal bath. Finally, (also) the nonequilibrium specific heat goes to zero exponentially fast with vanishing temperature, realizing an extended Third Law.