title: Critical behavior of the frustrated antiferromagnetic six-state clock model on a triangular lattice.
abstract: We study the antiferromagnetic six-state clock model with nearest neighbor interactions on a triangular lattice with extensive Monte Carlo simulations. We find clear indications of two phase transitions at two different temperatures: Below T(I) a chirality order sets in and by a thorough finite-size-scaling analysis of the specific heat and the chirality correlation length we show that this transition is in the Ising universality class (with a nonvanishing chirality order parameter below T(I)). At T(KT) (<T(I)) the spin-spin correlation length as well as the spin susceptibility diverges according to a Kosterlitz-Thouless (KT) form and spin correlations decay algebraically below T(KT). We compare our results to recent x-ray diffraction experiments on the orientational ordering of CF3Br monolayers physisorbed on graphite. We argue that the six-state clock model describes the universal feature of the phase transition in the experimental system and that the orientational ordering belongs to the KT universality class.
authors.affiliation: Theoretische Physik, Universität des Saarlandes, 66041 Saarbrücken, Germany.
authors.forename: J D
authors.initials: JD
authors.lastname: Noh
authors.forename: H
authors.initials: H
authors.lastname: Rieger
authors.forename: M
authors.initials: M
authors.lastname: Enderle
authors.forename: K
authors.initials: K
authors.lastname: Knorr