Thickness–Magnetic Field Phase Diagram at the Superconductor-Insulator Transition in 2D

Abstract

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