title: Phase diagram of a disordered boson Hubbard model in two dimensions.
abstract: We study the zero-temperature phase transition of a two-dimensional disordered boson Hubbard model. The phase diagram is constructed in terms of the disorder strength and the chemical potential. Via Monte Carlo simulations, we find a multicritical line separating the weak-disorder regime, where the Mott-insulator-to-superfluid transition occurs, from the strong-disorder regime, where the Bose-glass-to-superfluid transition occurs. On the multicritical line, the insulator-to-superfluid transition has the dynamical critical exponent z = 1.35+/-0.05 and the correlation length critical exponent nu = 0.67+/-0.03. We suggest that the proliferation of the particle-hole pairs screens out the weak-disorder effects.
authors.affiliation: School of Physics and Center for Theoretical Physics, Seoul National University, Seoul 151-742, Korea.
authors.forename: J W
authors.initials: JW
authors.lastname: Lee
authors.forename: M C
authors.initials: MC
authors.lastname: Cha
authors.forename: D
authors.initials: D
authors.lastname: Kim