title: Feshbach-stabilized insulator of bosons in optical lattices.
abstract: Feshbach resonances-namely, resonances between an unbound two-body (atomic) state and a bound (molecular) state, differing in magnetic moment-are a unique tool to tune the interaction properties of ultracold atoms. Here we show that the spin-changing interactions, coherently coupling the atomic and molecular states, can act as a novel mechanism to stabilize an insulating phase-the Feshbach insulator-for bosons in an optical lattice close to a narrow Feshbach resonance. Making use of quantum Monte Carlo simulations and mean-field theory, we show that the Feshbach insulator appears around the resonance, preventing the system from collapsing when the effective atomic scattering length becomes negative. On the atomic side of the resonance, the transition from condensate to Feshbach insulator has a characteristic first-order nature, due to the simultaneous loss of coherence in the atomic and molecular components. These features appear clearly in the ground-state phase diagram of, e.g., ^{87}Rb around its 414 G resonance, and they are therefore directly amenable to experimental observation.
authors.affiliation: Laboratoire de Physique, CNRS UMR 5672, École Normale Supérieure de Lyon, Université de Lyon, 46 Allée d'Italie, F-69364 Lyon, France.
authors.forename: L
authors.initials: L
authors.lastname: de Forges de Parny
authors.affiliation: Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: V G
authors.initials: VG
authors.lastname: Rousseau
authors.affiliation: Laboratoire de Physique, CNRS UMR 5672, École Normale Supérieure de Lyon, Université de Lyon, 46 Allée d'Italie, F-69364 Lyon, France.|Institut Universitaire de France, 103 boulevard Saint-Michel, 75005 Paris, France.
authors.forename: T
authors.initials: T
authors.lastname: Roscilde