Thickness-magnetic field phase diagram at the superconductor-insulator transition in 2d

The superconductor-insulator transition in ultrathin films of amorphous Bi has been tuned by changing both film thickness and magnetic field on the same set of films. A thickness-magnetic field phase diagram has been mapped in the T=0 limit. A finite size scaling analysis has been carried out to determine the critical exponent product νz, which was found to be 1.2±0.2 and 1.4±0.2 for the thickness-tuned transitions in zero and finite magnetic fields, respectively. These are different from the exponent found for the magnetic-field-tuned transition in the same system, 0.7±0.2.