1207.2349 (S. E. Korshunov)

Incommensurate vortices and phase transitions in two-dimensional XY
models with interaction having auxiliary minima    [PDF]

S. E. Korshunov

We show that contrary to the claim of Poderoso et al. [PRL 106, 067202 (2011)], phase diagrams of the two-dimensional XY models in which the interaction of nearest planar spins is a nonmonotonic function of the angle u between them, V(u) = - Jcos(u) - Kcos(qu), cannot include a phase transition related to the dissociation of pairs of fractional vortices if q > 2. Such a transition is possible in the case q = 2 when topological charges of all vortices (conventional and half-integer) are commensurate with each other. However, for integer q > 2 the presence of free incommensurate vortices leads to the replacement of a genuine phase transition by a smooth crossover.

View original: http://arxiv.org/abs/1207.2349