Abstract
We have made simultaneous measurements of the longitudinal and Hall resistivities for granular films of indium with different thicknesses ( 20, and 60 nm) and the normal-state resistivities at temperatures down to 0.5 K and in fields up to 7 T. A striking scaling behavior expressed as has been observed for all the films studied irrespective of and at fixed fields which are not close to a critical field In the mixed state ( and where is the transition temperature), the coefficient and exponent β are nearly independent of the field strength and the film thickness In the vicinity of the field-driven superconductor-insulator transition, we have found the unusual insulating region where and represent critical fields determined by and respectively, which tends to grow with increasing and/or decreasing This region is similar to one found previously by Paalanen, Hebard, and Ruel in amorphous thin films, and the present result is consistent with their notion that the insulating region corresponds to the Bose-glass insulator.
- Received 22 July 1996
DOI:https://doi.org/10.1103/PhysRevB.56.410
©1997 American Physical Society