The role of Coulomb interaction in superconducting NbTiN thin films

TL;DR

This study investigates how Coulomb interactions influence the superconducting properties of NbTiN thin films, revealing that increasing Ti content reduces Coulomb repulsion and enhances the critical temperature.

Contribution

It demonstrates the role of Coulomb interaction in tuning superconductivity in NbTiN films, supported by experimental data and theoretical analysis.

Findings

$T_c$ increases with Ti fraction $x$

Disorder-enhanced Coulomb interaction decreases with $x$

Superconductivity is affected by Coulomb interaction modifications

Abstract

We report on the superconducting properties of Nb$_{1-x}$Ti$_x$N thin films of thickness $\sim$ 10 nm, with different Ti fraction $x$ in the range $ 0 \leq x \leq 0.5$, deposited by high temperature chemical vapor deposition. In this parameter range, we observe that the superconducting critical temperature ($T_c$) increases with $x$. Our analysis, in accordance with both McMillan's and Finkelstein's theories, shows that disorder-enhanced Coulomb interaction decreases with $x$, leading to an increase of $T_c$.