Tricritical behavior of nonequilibrium Ising spins in fluctuating environments

Jong Min Park, Jae Dong Noh

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11 Scopus citations


We investigate the phase transitions in a coupled system of Ising spins and a fluctuating network. Each spin interacts with q neighbors through links of the rewiring network. The Ising spins and the network are in thermal contact with the heat baths at temperatures TS and TL, respectively, so the whole system is driven out of equilibrium for TS≠TL. The model is a generalization of the q-neighbor Ising model [A. Jȩdrzejewski, Phys. Rev. E 92, 052105 (2015)PLEEE81539-375510.1103/PhysRevE.92.052105], which corresponds to the limiting case of TL=∞. Despite the mean-field nature of the interaction, the q-neighbor Ising model was shown to display a discontinuous phase transition for q≥4. Setting up the rate equations for the magnetization and the energy density, we obtain the phase diagram in the TS-TL parameter space. The phase diagram consists of a ferromagnetic phase and a paramagnetic phase. The two phases are separated by a continuous phase transition belonging to the mean-field universality class or by a discontinuous phase transition with an intervening coexistence phase. The equilibrium system with TS=TL falls into the former case while the q-neighbor Ising model falls into the latter case. At the tricritical point, the system exhibits the mean-field tricritical behavior. Our model demonstrates a possibility that a continuous phase transition turns into a discontinuous transition by a nonequilibrium driving. Heat flow induced by the temperature difference between two heat baths is also studied.

Original languageEnglish
Article number042106
JournalPhysical Review E
Issue number4
StatePublished - 5 Apr 2017


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