# Superconductor to weak-insulator transitions in disordered Tantalum Nitride films

## TL;DR

This paper investigates the superconductor-insulator transition in disordered tantalum nitride films, revealing classical and quantum behaviors, critical scaling, and proposing a universal pattern at the boundary between superconducting and insulating states.

## Contribution

It provides experimental evidence of different SIT regimes in tantalum nitride films and introduces a universal behavior pattern at the superconductor-insulator boundary.

## Key findings

- Classical hopping transport in insulating films.
- Critical exponents consistent with classical percolation.
- Non-universal Hall resistivity at the transition.

## Abstract

We study the two-dimensional superconductor-insulator transition (SIT) in thin films of tantalum nitride. At zero magnetic field, films can be disorder-tuned across the SIT by adjusting thickness and film stoichiometry; insulating films exhibit classical hopping transport. Superconducting films exhibit a magnetic field-tuned SIT, whose insulating ground state at high field appears to be a quantum-corrected metal. Scaling behavior at the field-tuned SIT shows classical percolation critical exponents $z \nu \approx$ 1.3, with a corresponding critical field $H_c \ll H_{c2}$. The Hall effect shows a crossing point near $H_c$, but with a non-universal critical value $\rho_{xy}^c$ comparable to the normal state Hall resistivity. We propose that high-carrier density metals will always exhibit this pattern of behavior at the boundary between superconducting and (trivially) insulating ground states.