Phase diagram of a two-dimensional large-Q Potts model in an external field Original Research Article

We use a two-dimensional Wang–Landau sampling algorithm to map out the phase diagram of a Q-state Potts model with image in an external field H that couples to one state. Finite-size scaling analyses show that for large Q the first-order phase transition point at image is in fact a triple point at which three first-order phase transition lines meet. One such line is restricted to image; another line has image. The third line, which starts at the image triple point, ends at a critical point image which needs to be located in a two-dimensional parameter space. The critical field image is positive and decreases with decreasing Q, which is in qualitative agreement with previous predictions.