A zero-temperature magnetic-field-tuned superconducting-insulating transition is observed in two-dimensional $a$-MoGe films. The low temperature transport properties of these films show scaling behavior consistent with a transition driven by long-range Coulomb interactions and quantum phase fluctuations in a two-dimensional superconductor. However, contrary to the theoretical predictions we find the critical resistance to be sample dependent. We suggest that the apparent lack of universality in the critical resistance is due to the finite contribution of fermionic excitations to the resistance.

• Received 29 November 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.3037