On the order of the phase transition in the spin-1 Baxter–Wu model

Abstract

In this work we investigate the order of the phase transition of the spin-1 Baxter–Wu model. We used extensive entropic simulations to describe the behavior of quantities which reveal the order of the phase transition. We applied finite-size scaling laws for continuous and discontinuous phase transitions. Our results show that this system exhibits an indeterminacy regarding the order of the phase transition, i.e., the results are conclusive for both transitions, whether continuous or discontinuous. In such a scenario we carried out a study of the configurations in the region of the phase transition, which confirmed that the model seems to undergo a tetracritical transition, with the coexistence of a ferromagnetic and three ferrimagnetic configurations, suggesting that it may be a multicritical point, where the continuous and the discontinuous phase transitions may coexist reflecting different features of the system. We propose a new way of carrying out the entropic simulations where two densities of states are generated simultaneously, for the ferro- and the ferrimagnetic states. The behavior of the energy probability distribution, the inverse temperature, and the magnetizations for each state confirms the coexistence of the discontinuous and the continuous phase transitions.