Supercapacitance and superinductance of TiN and NbTiN films in the vicinity of superconductor-to-insulator transition.

We investigate the low-temperature complex impedance of disordered insulating thin TiN and NbTiN films in the frequency region 400 Hz-1 MHz in close proximity to the superconductor-insulator transition (SIT). The frequency, temperature, and magnetic field dependencies of the real and imaginary parts of the impedance indicate that in full accord with the theoretical predictions and earlier observations, the films acquire self-induced electronic granularity and become effectively random arrays of superconducting granules coupled via Josephson links. Accordingly, the inductive component of the response is due to superconducting droplets, while the capacitive component results from the effective Josephson junctions capacitances. The impedance crosses over from capacitive to inductive behavior as films go across the transition.

Superconducting phase transitions in disordered NbTiN films.

Suppression of superconductivity in disordered systems is a fundamental problem of condensed matter physics. Here we investigate superconducting niobium-titanium-nitride (Nb1-xTixN) thin films grown by the atomic layer deposition (ALD) with slightly different growth process parameters. We observe a smooth crossover from the disorder-driven superconductor-normal metal transition (SMT) to the superconductor-insulator transition (SIT) via the intermediate Bose metal state detected by the low-temperature saturation of the temperature dependence of the sheet resistance. We demonstrate that the SIT via the intervening Bose metal state occurs if the sheet resistance of the film in the maximum, Rmax prior to the superconducting drop of R(T), exceeds Rq = h/4e2.

Quantum contributions to the magnetoconductivity of critically disordered superconducting TiN films.

The onset of superconductivity in the presence of disorder is a fundamental problem of condensed matter physics. Here we investigate the magnetoconductance of disordered ([Formula: see text]) superconducting TiN films above the critical temperature T c. We show that the magnetoconductivity of moderately disordered films with [Formula: see text] is in full agreement with the perturbative theory of quantum contributions to conductivity. We demonstrate that the magnetoconductivity of films with [Formula: see text] is also in agreement with the perturbative theory down to temperatures [Formula: see text]. The quantitative discrepancy between experiment and theory develops only below temperatures [Formula: see text] for films with [Formula: see text]. This discrepancy can be eliminated if we assume steeper temperature dependence of the Larkin's electron-electron attraction strength, [Formula: see text]. The obtained temperature dependence of electron phase breaking time [Formula: see text] is in agreement with theoretical predictions for all samples.