Mott insulator to superfluid transition of ultracold bosons in an optical lattice near a Feshbach resonance

¹ Department of Physics, Yale University - New Haven, CT-06520-8120, USA
² Laboratoire de Physique des Solides, CNRS UMR 8502, Université Paris-Sud 91405 Orsay, France

Received: 15 December 2004
Accepted: 31 March 2005

Abstract

We study the phase diagram of ultracold bosons in an optical lattice near a Feshbach resonance. Depending on the boson density, the strength of the optical-lattice potential and the detuning from resonance, the ground state can be a Mott insulator, a superfluid phase with both an atomic and a molecular condensate, or a superfluid phase with only a molecular condensate. Mott insulator to superfluid transitions can be induced either by decreasing the strength of the optical-lattice potential or by varying the detuning from the Feshbach resonance. Quite generally, we find that for a commensurate density the ground state may undergo several insulator-superfluid or superfluid-insulator transitions as the magnetic field is varied through the resonance.