Helicity modulus near a three-state Potts-like transition

By employing Monte Carlo simulations, both the helicity modulus and the heat capacity of a coupled classical XY model in two dimensions have been calculated. The model is based on the Hamiltonian proposed by Bruinsma and Aeppli [Phys. Rev. Lett. 48, 1625 (1982)]. For the first time, the model enables us to study the temperature dependence of the helicity modulus and obtain the associated critical exponent near a three-state Potts transition