Superconducting fluctuations and characteristic time scales in amorphous WSi

Abstract

We study magnitudes and temperature dependences of the electron-electron and electron-phonon interaction times which play the dominant role in the formation and relaxation of photon induced hotspot in two dimensional amorphous WSi films. The time constants are obtained through magnetoconductance measurements in perpendicular magnetic field in the superconducting fluctuation regime and through time-resolved photoresponse to optical pulses. The excess magnetoconductivity is interpreted in terms of the weak-localization effect and superconducting fluctuations. Aslamazov-Larkin, and Maki-Thompson superconducting fluctuation alone fail to reproduce the magnetic field dependence in the relatively high magnetic field range when the temperature is rather close to Tc because the suppression of the electronic density of states due to the formation of short lifetime Cooper pairs needs to be considered. The time scale τ_i of inelastic scattering is ascribed to a combination of electron-electron (τ_(e-e)) and electron-phonon (τ_(e-ph)) interaction times, and a characteristic electron-fluctuation time (τ_(e-fl)), which makes it possible to extract their magnitudes and temperature dependences from the measured τ_i. The ratio of phonon-electron (τ_(ph-e)) and electron-phonon interaction times is obtained via measurements of the optical photoresponse of WSi microbridges. Relatively large τ_(e-ph)/τ_(ph-e) and τ_(e-ph)/τ_(e-e) ratios ensure that in WSi the photon energy is more efficiently confined in the electron subsystem than in other materials commonly used in the technology of superconducting nanowire single-photon detectors (SNSPDs). We discuss the impact of interaction times on the hotspot dynamics and compare relevant metrics of SNSPDs from different materials.

References in corpus (6)

• Theory of single photon detection by 'dirty' current-carrying superconducting strip based on the kinetic equation approach
• Characteristics of superconducting tungsten silicide WxSi1-x for single photon detection
• Detection Mechanism in SNSPD: Numerical Results of a Conceptually Simple, Yet Powerful Detection Model
• Hotspot Relaxation Dynamics in a Current Carrying Superconductor
• Non-bolometric bottleneck in electron-phonon relaxation in ultra-thin WSi film
• Rise times of voltage pulses in NbN superconducting single-photon detectors

Cited by in corpus (7)

• Electron energy relaxation in disordered superconducting NbN films
• Determining the depairing current in superconducting nanowire single-photon detectors
• Preparation and Characterization of High-Entropy Alloy (TaNb)${}_{1-x}$(ZrHfTi)${}_x$ Superconducting Films
• Probing electron-electron interaction along with superconducting fluctuations in disordered TiN thin films
• Size dependent nature of the magnetic-field driven superconductor-to-insulator quantum-phase transitions
• Strong suppression of the resistivity near the transition to superconductivity in narrow micro-bridges in external magnetic fields
• Impact of helium ion irradiation on the thermal properties of superconducting nanowire single-photon detectors