High field termination of a Cooper-pair insulator

TL;DR

This study investigates how disorder affects the magnetic field-induced transition from superconducting to insulating states in amorphous indium oxide films, revealing the role of Cooper pairing in the insulating peak.

Contribution

It demonstrates the correlation between the critical magnetic field and the insulating peak, highlighting the significance of Cooper pairing in high-field insulating behavior.

Findings

Higher disorder samples show an insulating peak at high magnetic fields.

The insulating peak coincides with the critical field of less disordered samples.

Beyond the peak, resistance becomes weakly dependent on magnetic field.

Abstract

We conducted a systematic study of the disorder dependence of the termination of superconductivity, at high magnetic fields (B), of amorphous indium oxide films. Our lower disorder films show conventional behavior where superconductivity is terminated with a transition to a metallic state at a well-defined critical field, Bc2. Our higher disorder samples undergo a B-induced transition into a strongly insulating state, which terminates at higher B's forming an insulating peak. We demonstrate that the B terminating this peak coincides with Bc2 of the lower disorder samples. Additionally we show that, beyond this field, these samples enter a different insulating state in which the magnetic field dependence of the resistance is weak. These results provide crucial evidence for the importance of Cooper-pairing in the insulating peak regime.