|
G. Pupillo, H.P. Buechler, A. Micheli, M. Lukin, E. Demler, N.V. Prokof'ev, P.
Zoller
In this talk we address the strongly interacting regime of an ensemble of dipoles in two dimensions. We show the existence of a quantum phase transition from a superfluid to a triangular crystal, driven by the competition of interaction and kinetic energies. We analyze the phase diagram by means of analytic estimates and quantum Monte-Carlo simulations for the case of repulsive dipolar interactions. As a specific realization we consider polar molecules confined in a plane by a tight one-dimensional optical lattice. Applying an electric field allows to induce a finite dipole moment perpendicular to the plane, which yields the characteristic repulsive long-range dipolar shape of the interactions. However, the internal structure of the polar molecules also allows for tailoring the long-range part of the interactions by using a microwave field. We show that this enables one to engineer a wide variety of potentials which include e.g. hard-core repulsion, and potentials which are attractive at long distances, while strongly repulsive at short distances. Finally, we analyze the experimentally relevant case of a mesoscopic number of particles confined in an additional in-plane parabolic potential. We show that for the purely repulsive dipolar potential it is possible to realize lattice geometries which can differ significantly from the triangular one. The use of a microwave field can be used to modify the lattice spacing. We discuss the possibility to realize these systems utilizing Rydberg states of alkali atoms. |
|