Quantum phase transition in a two-dimensional system of dipoles.
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.
Astrakharchik
G E
GE
Departament de Física i Enginyeria Nuclear, Campus Nord B4-B5, Universitat Politècnica de Catalunya, E-08034 Barcelona, Spain.
Boronat
J
J
Kurbakov
I L
IL
Lozovik
Yu E
YE