Gate voltage modulation of the superconducting state in a degenerate semiconductor

TL;DR

This study shows that applying a gate voltage can significantly modulate the superconducting transition temperature and supercurrent in epitaxial Indium Nitride, highlighting carrier density as a key factor in superconductivity.

Contribution

It demonstrates gate voltage control of superconductivity in InN, revealing carrier density as the primary influence over transition temperature and supercurrent suppression.

Findings

Carrier density modulation alters Tc by up to 204 mK.

Observed 60% bipolar supercurrent suppression.

Behavior consistent with BCS s-wave superconductivity.

Abstract

In this work, we demonstrate that the modulation of carrier density can alter the superconducting transition temperature by up to $204$ mK in epitaxial Indium Nitride on Gallium Nitride, accounting for the $10$% of the transition temperature in ungated conditions. Our samples are likely free from strong localization effects and significant granularity, as indicated by $( k_{f l} \gg 1 )$, suggesting that the primary determinant of the transition temperature in InN is carrier density, rather than disorder scattering. The observed behavior is consistent with BCS s-wave superconductivity, corroborated by the superconducting parameters we measured. Furthermore, we observed a $60$% bipolar suppression of the supercurrent in our experiments.