Critical behavior of the six-state clock model in two dimensions

We have examined the critical properties of the q=6 clock (vector Potts) model in two dimensions through Monte Carlo simulations. The model was investigated on L\ifmmode\times\else\texttimes\fi{}L square lattices of size L=4 to L=72 with periodic boundary conditions. We found an intermediate XY-like phase between a low-temperature ordered phase and a high-temperature disordered phase. The phase transitions occur at ${k}_{B}$${T}_{1}$/J=0.68\ifmmode\pm\else\textpm\fi{}0.02 and ${k}_{B}$${T}_{2}$/J=0.92\ifmmode\pm\else\textpm\fi{}0.01 and are of the Kosterlitz-Thouless type. The susceptibility diverges in the intermediate phase and the exponent \ensuremath{\eta} varies between 0.100 at ${T}_{1}$ and 0.275 at ${T}_{2}$.