Signature of Cooper Pairs in the Non-Superconducting Phases of Amorphous Superconducting Tantalum Films

TL;DR

This study investigates amorphous tantalum films, revealing evidence of localized Cooper pairs in both insulating and metallic phases, suggesting their persistence beyond superconductivity.

Contribution

It provides experimental evidence for the presence of Cooper pairs in non-superconducting phases of amorphous tantalum films, expanding understanding of pairing in disordered systems.

Findings

Localized Cooper pairs exist in insulating phases.

Cooper pairs also persist in metallic ground states.

Non-monotonic transport behavior indicates pairing phenomena.

Abstract

We have studied the magnetic field or disorder induced insulating and metallic phases in amorphous Ta superconducting thin films. The evolution of the nonlinear transport in the insulating phase exhibits a non-monotonic behavior as the magnetic field is increased. We suggest that this observation could be an evidence of the presence of localized Cooper pairs in the insulating phase. As the metallic phase intervenes the superconducting and insulating states in Ta films, this result further reveals that Cooper pairs also exist in the metallic ground state.