Latent heat calculation of the three-dimensional $q=3,$ 4, and 5 Potts models by the tensor product variational approach

Three-dimensional (3D) q-state Potts models $(q=3,$ 4, and 5) are studied by the tensor product variational approach, which is a recently developed variational method for 3D classical lattice models. The variational state is given by a 2D product of local factors, and is improved by way of self-consistent calculations assisted by the corner transfer matrix renormalization group. It should be noted that no a priori condition is imposed for the local factor. Transition temperatures and latent heats are calculated from the observations of thermodynamic functions in both ordered and disordered phases.