Phase transitions of the four-state Potts model on the square and honeycomb lattices

It is widely believed that the phase transition for the four-state ferromagnetic Potts model on the square lattice is of pseudo-first order. Specifically, it is expected that first-order phase transition behavior is found on small lattices and that the true nature of the second-order phase transition only emerges with large system sizes. It is also intuitively expected that, for other geometries, the types of the associated phase transitions should be identical to that of the square lattice. However, after simulating more than 16 million spins for the four-state Potts model, we observe that a feature of the first-order phase transition persists on the square lattice. Additionally, a characteristic of the second-order phase transition already appears on a small honeycomb lattice. Indications of a pseudo-first-order phase transition were not found in our investigation. This suggests that a thorough analytic calculation may be required to develop a better understanding of the presented results.