Hyperactivated resistance in TiN films on the insulating side of the disorder-driven superconductor-insulator transition

TL;DR

This study explores the insulating phase near the superconductor-insulator transition in TiN films, revealing a complex resistance behavior influenced by temperature and magnetic fields, including a transition to a quantum resistance regime.

Contribution

It provides new insights into the resistance mechanisms and magnetic field effects in TiN films close to the superconductor-insulator transition.

Findings

Resistance shows a crossover from logarithmic to activated behavior with temperature.

At ultralow temperatures, resistance increases faster than thermally activated predictions.

High magnetic fields lead to saturation of magnetoresistance near quantum resistance.

Abstract

We investigate the insulating phase that forms in a titanium nitride film in a close vicinity of the disorder-driven superconductor-insulator transition. In zero magnetic field the temperature dependence of the resistance reveals a sequence of distinct regimes upon decreasing temperature crossing over from logarithmic to activated behavior with the variable-range hopping squeezing in between. In perpendicular magnetic fields below 2 T, the thermally activated regime retains at intermediate temperatures, whereas at ultralow temperatures, the resistance increases faster than that of the thermally activated type. This indicates a change of the mechanism of the conductivity. We find that at higher magnetic fields the thermally activated behavior disappears and the magnetoresistive isotherms saturate towards the value close to quantum resistance h/e^2.