Enhanced superconductivity and superconductor to insulator transition in nano-crystalline molybdenum thin films

TL;DR

This study investigates how disorder influences superconductivity and the superconductor-insulator transition in nano-crystalline molybdenum thin films, revealing enhanced superconductivity and a transition driven by disorder.

Contribution

It demonstrates the control of grain size via deposition pressure and correlates disorder with the superconductor-insulator transition in molybdenum thin films.

Findings

Disorder induces superconductor-insulator transition.

Enhanced superconductivity observed at certain disorder levels.

Ioffe-Regel parameter correlates with the transition.

Abstract

Disorder driven superconductor to insulator transition via intermediate metallic regime is reported in nano-crystalline thin films of molybdenum. The nano-structured thin films have been deposited at room temperature using DC magnetron sputtering at different argon pressures. The grain size has been tuned using deposition pressure as the sole control parameter. A variation of particle sizes, room temperature resistivity and superconducting transition has been studied as a function of deposition pressure. The nano-crystalline molybdenum thin films are found to have large carrier concentration but very low mobility and electronic mean free path. Hall and conductivity measurements have been used to understand the effect of disorder on the carrier density and mobilities. Ioffe-Regel parameter is shown to correlate with the continuous metal-insulator transition in our samples.