title: Absence of a direct superfluid to mott insulator transition in disordered bose systems.
abstract: We prove the absence of a direct quantum phase transition between a superfluid and a Mott insulator in a bosonic system with generic, bounded disorder. We also prove the compressibility of the system on the superfluid-insulator critical line and in its neighborhood. These conclusions follow from a general theorem of inclusions, which states that for any transition in a disordered system, one can always find rare regions of the competing phase on either side of the transition line. Quantum Monte Carlo simulations for the disordered Bose-Hubbard model show an even stronger result, important for the nature of the Mott insulator to Bose glass phase transition: the critical disorder bound Delta(c) corresponding to the onset of disorder-induced superfluidity, satisfies the relation Delta(c)>Eg/2, with Eg/2 the half-width of the Mott gap in the pure system.
authors.affiliation: Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: L
authors.initials: L
authors.lastname: Pollet
authors.forename: N V
authors.initials: NV
authors.lastname: Prokof'ev
authors.forename: B V
authors.initials: BV
authors.lastname: Svistunov
authors.forename: M
authors.initials: M
authors.lastname: Troyer