Probing electron-electron interaction along with superconducting fluctuations in disordered TiN thin films

Abstract

In two-dimensional (2D) disordered superconductors prior to superconducting (SC) transition, the appearance of a resistance peak in the temperature dependent resistance R(T) measurements indicates the presence of weak localization (WL) and electron-electron interaction (EEI) in the diffusion channel and SC fluctuations in the Cooper channel. Here, we demonstrate an interplay between SC fluctuations and EEI by low-temperature magnetotransport measurements for a set of 2D disordered TiN thin films. While cooling the sample, a characteristic temperature T* is obtained from the R(T) at which SC fluctuations start to appear. The upturn in R(T) above T* corresponds to WL and/or EEI. By the temperature and field dependences of the observed resistance, we show that the upturn in R(T) originates mainly from EEI with a negligible contribution from WL. Further, we have used the modified Larkin's electron-electron attraction strength β(T/Tc), containing a field-induced pair-breaking parameter, in the Maki-Thompson SC fluctuation term. Here, the temperature dependence of β(T/Tc) obtained from the magnetoresistance (MR) analysis shows a diverging behavior close to Tc, and it remains almost constant at higher temperature within the limit of ln(T/Tc)<1. Interestingly, the variation of β(T/Tc) on the reduced temperature (T/Tc) offers a common trend which has been closely followed by all the concerned samples presented in this paper. Finally, the temperature dependence of inverse phase scattering time (τϕ−1), as obtained from the MR analysis, clearly shows two different regimes; the first one close to Tc follows the Ginzburg-Landau relaxation rate (τGL−1), whereas the second one at high temperature varies almost linearly with temperature, indicating the dominance of inelastic electron-electron scattering for the dephasing mechanism. These two regimes are followed in a generic way by all the samples despite being grown under different growth conditions.

Source-reported materials — not catalogue approval

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