Phase diagrams of surface structures from Bethe-ansatz solutions of the quantum sine-Gordon model

Phase diagrams of uniaxial two-dimensional systems with commensurate, incommensurate, and liquid phases are derived by combining exact results for the quantum sine-Gordon model with the Kosterlitz-Thouless theory of melting. The phase diagram depends on the order of commensurability, p. In particular, for p=3 (the "chiral Potts" case), we conjecture that the phase diagram contains no Lifshitz point, in contrast to previous authors; for p=1, dislocations remove the original CI transition completely.