No abstract

We use quantum Monte Carlo techniques to study a one-dimensional, disordered, interacting, Bose Hamiltonian. The effect of disorder on the Mott-insulator portion of the phase diagram is determined. We observe the destruction of superfluidity by disorder at incommensurate densities, for the first time demonstrating the emergence of a "Bose-glass" phase. In addition to these strong-coupling phases, we observe an unanticipated reentrance into an Anderson-type localized regime for weak couplings.

We study numerically the motion of vortices in dirty type II superconductors. In two dimensions at strong driving currents, vortices form highly correlated "static channels." The static structure factor exhibits convincing scaling behavior, demonstrating quasi-long-range translational order in the transverse direction. However, order in the longitudinal direction is only short range. We clearly establish the existence of a finite transverse critical current, suggesting strong barriers against transverse driving forces. We discuss these results in terms of recently proposed theories of the moving vortex systems.

We use quantum Monte Carlo techniques to study the critical properties of an interacting-boson model in one dimension. The phase diagram consists of a series of (Mott-) insulating phases at commensurate fillings and a superfluid phase. From the critical behavior of the superfluid density and the compressibility we measure the exponents v and z, which agree with predictions based on a scaling analysis.