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 $T=0\mathrm{}$ limit. A finite size scaling analysis has been carried out to determine the critical exponent product $\nu z$, which was found to be $1.2\pm 0.2$ and $1.4\pm 0.2$ 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, $0.7\pm 0.2$.