Journal of Statistical Physics, Vol. 82, Nos. 1/2, 1996. p. 1-29.
We calculate the interfacial tension of the N-state chiral Potts model by solving the functional relations for the transfer matrices of the model with skewed boundary conditions. Our result is valid for the general physical model (with positive Boltzmann weights) and at all subcritical temperatures. The interracial tension has been calculated previously for the superintegrable chiral Potts model with skewed boundary conditions. Using Z-invariance, Baxter has argued that the interfacial tension of this model should be the same as the interfacial
tension of the general physical model. We show that this is indeed the case.