Phase transitions of two spin-1/2 Baxter–Wu layers coupled with Ising-type interactions

Abstract

Using a Monte Carlo simulation and the single histogram reweighting technique, we study the critical behaviors and phase transitions of the Baxter–Wu (BW) model on a two-layer triangular lattice with Ising-type interlayer couplings. Via the finite-size analysis, we obtain the transition temperatures and critical exponents at repulsive and attractive interlayer couplings. The data for the repulsive interlayer coupling suggest continuous transitions, and the critical behaviors are the same as those of the 2D BW model, belonging to the four-state Potts universality class. The reduced energy cumulants and the histograms reveal that attractive coupling leads to weak first-order phase transitions. The pseudocritical exponents with the existence of the interlayer couplings indicate that the first-order transition is very close to the critical point of the 2D standard BW model.