Superconductor-insulator transition in a parallel magnetic field

Wenhao Wu, Louisiana State University
P. W. Adams, Louisiana State University


We report the use of a parallel magnetic field to suppress the superconducting gap and intergrain Josephson coupling in granular Al films. The critical field Hc is spin paramagnetically limited, and the field induced superconductor-insulator (S-I) transition is found to go from second order to first order at 250 mK. In the vicinity of Hc, the field reproduces the quasireentrance and super-resistive behavior seen in the zero-field S-I transition. We show that the super-resistive phase is dominated by Coulomb blockade. © 1994 The American Physical Society.