Superconductor-insulator transition in two dimensions

The superconductor-insulator transition of ultrathin films of bismuth, grown on liquid-helium-cooled substrates, has been studied. The transition was tuned by changing both film thickness and perpendicular magnetic field. Assuming that the transition is controlled by a $T=0$ critical point, a finite-size scaling analysis was carried out to determine the correlation length exponent {ν} and the dynamical critical exponent $z.$ The phase diagram and the critical resistance have been studied as a function of film thickness and magnetic field. The results are discussed in terms of bosonic models of the superconductor-insulator transition, as well as the percolation models which predict finite dissipation at $T=0.$