title: Quantum phase transition in a two-dimensional system of dipoles.
abstract: The ground-state phase diagram of a two-dimensional Bose system with dipole-dipole interactions is studied by means of a quantum Monte Carlo technique. Our calculation predicts a quantum phase transition from a gas to a solid phase when the density increases. In the gas phase, the condensate fraction is calculated as a function of the density. Using the Feynman approximation, the collective excitation branch is studied and the appearance of a roton minimum is observed. The results of the static structure factor at both sides of the gas-solid phase are also presented. The Lindemann ratio at the transition point becomes gamma=0.230(6). The condensate fraction in the gas phase is estimated as a function of the density.
authors.affiliation: Departament de Física i Enginyeria Nuclear, Campus Nord B4-B5, Universitat Politècnica de Catalunya, E-08034 Barcelona, Spain.
authors.forename: G E
authors.initials: GE
authors.lastname: Astrakharchik
authors.forename: J
authors.initials: J
authors.lastname: Boronat
authors.forename: I L
authors.initials: IL
authors.lastname: Kurbakov
authors.forename: Yu E
authors.initials: YE
authors.lastname: Lozovik