Superconductor-insulator transition in two-dimensional dirty boson systems

Universal properties of the zero-temperature superconductor-insulator transition in two-dimensional amorphous films are studied by extensive Monte Carlo simulations of bosons in a disordered medium. We report results for both short-range and long-range Coulomb interactions for several different points in parameter space. In all cases we observe a transition from a superconducting phase to an insulating Bose glass phase. From finite-size scaling of our Monte Carlo data we determine the universal conductivity ${\mathrm{\ensuremath{\sigma}}}^{\mathrm{*}}$ and the critical exponents at the transition. The result ${\mathrm{\ensuremath{\sigma}}}^{\mathrm{*}}$=(0.55\ifmmode\pm\else\textpm\fi{}0.66)(2e${)}^{2}$/h for bosons with long-range Coulomb interaction is roughly consistent with experiments reported so far. We also find ${\mathrm{\ensuremath{\sigma}}}^{\mathrm{*}}$=(0.14\ifmmode\pm\else\textpm\fi{}0.03)(2e${)}^{2}$/h for bosons with short-range interactions.