Superconductivity in amorphous RexZr (x ~ 6) thin films

TL;DR

This paper reports the growth and detailed superconducting characterization of amorphous RexZr (x ~ 6) thin films, revealing robust superconductivity down to nanometer thicknesses and evidence for strong coupling s-wave pairing.

Contribution

It introduces a new amorphous RexZr superconductor in thin film form and provides comprehensive measurements of its superconducting properties and phase diagram.

Findings

Superconducting transition temperature (Tc) of 5.9 K for films >40 nm

Superconductivity persists down to 8 nm thickness with marginal property changes

Evidence for strong coupling s-wave superconductivity and vortex liquid phases

Abstract

We report the growth, characterization and superconducting properties of a new amorphous superconductor, RexZr ( x ~ 6 ), in thin film form. Films were grown by pulsed laser deposition with the substrate kept at room temperature. Films with thickness larger than 40 nm showed a superconducting transition temperature (Tc) of 5.9 K. Superconducting properties were measured for films with varying thickness from 120 to 3 nm. The normal state resistance scales linearly with inverse of thickness. The transition temperature, critical field, coherence length, penetration depth and superconducting energy gap changes marginally with decreasing film thickness down to 8 nm. Scanning tunneling spectroscopy and penetration depth measurements provide evidence for a single gap strong coupling s-wave superconductor. Magneto-transport properties indicate a rich magnetic field-temperature phase diagram with the possibility of vortex liquid phases existing over a large fraction of the mixed state.