Superconductivity in the insulating phase above the field-tuned superconductor-insulator transition in disordered indium oxide films

We study the insulating phase of disordered indium oxide films that undergo a field-tuned superconductor-insulator transition. The transport measurements in a perpendicular magnetic field show distinct regimes of strongly fluctuating order-parameter amplitude and phase, and reveal a wide range of insulator strength in samples with differing disorder, despite the similarity in behavior near the SIT. We characterize the strength of the insulating phase and compare it to the superconducting strength. We find that the films do not return to the expected normal state even at high perpendicular magnetic fields where all pairs should be broken, suggesting the remaining presence of superconductivity at high fields. (c) 2005 Elsevier B.V. All rights reserved.