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

Abstract

In 2D disordered superconductors prior to superconducting transition, the appearance of a resistance peak in the temperature dependent resistance [R(T)] measurements indicates the presence of weak localization (WL) & electron-electron interaction (EEI) in diffusion channel and superconducting fluctuations in the Cooper channel. Here, we demonstrate an interplay between superconducting fluctuations and electronelectron interaction by low temperature magnetotransport measurements for a set of 2D disordered TiN thin films. While cooling down the sample, a characteristic temperature T* is obtained from the R(T) at which superconducting 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 (MT) superconducting fluctuation term. Here, the temperature dependence of the β(T/Tc) obtained from the magnetoresistance 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 study. Finally, the temperature dependence of inverse phase scattering time (𝜏 𝜙 −1 ), as obtained from the magnetoresistance analysis, clearly shows two different regimes; the first one close to Tc follows the Ginzburg-Landau relaxation rate (𝜏 𝐺𝐿 −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 in spite of being grown under different growth conditions.

Granularity mediated multiple reentrances with negative magnetoresistance in disordered TiN thin films

“…With dominating DOS contribution, resistance maximum can appear at higher temperature. Under the application of magnetic field, MT gets suppressed and the resistance maximum is expected to move towards lower temperature with reduced amplitude 6 , 30 as observed in the present study.…”

“…Finally, the sputtered samples were transferred in situ to an UHV chamber attached to the sputtering chamber for annealing which was done at ~ 780 °C for 2 h in a high vacuum condition with pressure less than 2 × 10 −7 Torr. It is noteworthy to mention that the annealing pressure here is much higher than the pressure (< 5 × 10 −8 Torr) maintained during the annealing for the samples presented in our previous reports 30 , 55 . Hence, oxygen content in the present batch is expected to be more and it may have significant influence on the transport properties of the sample.…”

“…In this article, we report the observation of multiple reentrant resistive states in the zero-field R ( T ) measurements for granular TiN thin film above the T c . Here, each of the reentrant resistive states is associated with a resistance peak that appears for the temperature range where the contributions from SFs to the conductivity correction are expected to be significant 30 , 31 . Under an external magnetic field, the resistance peaks get suppressed as observed in the field dependent R ( T ) which indicates the EEI might not be the origin behind the observed resistance peaks 30 .…”

“…Here, each of the reentrant resistive states is associated with a resistance peak that appears for the temperature range where the contributions from SFs to the conductivity correction are expected to be significant 30 , 31 . Under an external magnetic field, the resistance peaks get suppressed as observed in the field dependent R ( T ) which indicates the EEI might not be the origin behind the observed resistance peaks 30 . Further, magnetic field dependent resistance R ( B ) measurements, carried out in both perpendicular and parallel field directions, also feature multiple reentrances that evolve with temperature.…”