Physical review. B, Condensed matter
Phase structure and dual properties of ZN -symmetric models on a triangular lattice
Robert S. Savit
Abstract
Motivated by the search for physical two-dimensional systems with the unusual phase structure of the vector Potts (clock) model, we study two ${Z}_{N}$-symmetric periodic Gaussian models (PGM) on a triangular lattice. The models differ from each other only in their vortex structure, and should be in the same universality class, along with the $N$-state clock model. One of the models is self-dual. We also argue that the critical inverse temperature of the Gaussian approximation to the $\mathrm{XY}$ model on a square lattice, ${\ensuremath{\beta}}_{\ensuremath{\square}}^{*}$, should be related to ${\ensuremath{\beta}}_{\ensuremath{\Delta}}^{*}$, the critical inverse temperature of a similar model on a triangular lattice, by ${\ensuremath{\beta}}_{\ensuremath{\Delta}}^{*}\sqrt{3}={\ensuremath{\beta}}_{\ensuremath{\square}}^{*}$. Using this result and the self-dual property of one of our ${Z}_{N}$ PGM's, we find that the equation determining ${N}_{c}$, the value of $N$ above which there must be at least two phase transitions, is identical for the self-dual ${Z}_{N}$ PGM's on a square and triangular lattice.