title: Anomalous behavior of spin systems with dipolar interactions.
abstract: We study the properties of spin systems realized by cold polar molecules interacting via dipole-dipole interactions in two dimensions. Using a spin wave theory, that allows for the full treatment of the characteristic long-distance tail of the dipolar interaction, we find several anomalous features in the ground state correlations and the spin wave excitation spectrum, which are absent in their counterparts with short-range interaction. The most striking consequence is the existence of true long-range order at finite temperature for a two-dimensional phase with a broken U(1) symmetry.
authors.affiliation: Institute for Theoretical Physics III, University of Stuttgart, Stuttgart, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Peter
authors.forename: S
authors.initials: S
authors.lastname: Müller
authors.forename: S
authors.initials: S
authors.lastname: Wessel
authors.forename: H P
authors.initials: HP
authors.lastname: Büchler