Intrinsic non-linear conduction in the super-insulating state of thin TiN films

TL;DR

This study explores the non-linear electrical conduction phenomena in thin TiN films near the superconductor-insulator transition, revealing size-dependent activation energies and electron heating effects at ultra-low temperatures.

Contribution

It provides new experimental evidence of size-dependent activation energy and non-linear conduction mechanisms in super-insulating TiN films near the transition.

Findings

Arrhenius conductance with size-dependent activation energy

Large current jumps indicating electron heating effects

Power-law I-V behavior with temperature-dependent exponent

Abstract

We investigate experimentally the electric transport at the insulating side of the superconductor to insulator transition in thin TiN-films. At temperatures T > 50 mK we observe an Arrhenius-type conductance, with an activation energy depending logarithmically on the sample size. At high bias the current voltage (I-V) characteristics display a large current jump into an electron heating dominated regime. For the largest samples, and below 50 mK we observe a low-bias power law I ~ V^alpha characteristics with an exponent alpha > 1 rapidly growing with decreasing temperature, which is expected for a binding-unbinding crossover of the charge-Berezinskii-Kosterlitz-Thouless type.