Phonon heat capacity and self-heating normal domains in NbTiN nanostrips

Abstract

Self-heating normal domains in thin superconducting NbTiN nanostrips were characterized via steady-state hysteretic current-voltage characteristics measured at different substrate temperatures. The temperature dependence and the magnitude of the current, which sustains a domain in equilibrium at different voltages, can only be explained with a phonon heat capacity noticeably less than expected for 3-d Debye phonons. This reduced heat capacity coincides with the value obtained earlier from magnetoconductance and photoresponse studies of the same films. The rate of heat flow from electrons at a temperature Te to phonons in the substrate at a temperature TB is proportional to (T_e^p - T_B^p) with the exponent p~3, which differs from the exponents for heat flows mediated by the electron-phonon interaction or by escaping of 3-d Debye phonons via the film/substrate interface. We attribute both findings to the effect of the mean grain size on the phonon spectrum of thin granular NbTiN films. Our findings are significant for understanding the thermal transport in superconducting devices exploiting thin granular films.

References in corpus (8)

• Electron energy relaxation in disordered superconducting NbN films
• Hysteresis in superconducting short weak links and $\mu$-SQUIDs
• Retrapping Current, Self-Heating, and Hysteretic Current-Voltage Curves in Ultra-Narrow Superconducting Aluminum Nanowires
• Self-Heating Hotspots in Superconducting Nanowires Cooled by Phonon Black-Body Radiation
• Proximity effect model of ultra-narrow NbN strips
• Asymmetry in the effect of magnetic field on photon detection and dark counts in bended nanostrips
• Thermal relaxation in titanium nanowires: signatures of inelastic electron-boundary scattering in heat transfer
• Thermal relaxation in metal films limited by diffuson lattice excitations of amorphous substrates

Cited by in corpus (6)

• Observation of giant two-level systems in a granular superconductor
• Low-Temperature Heat Transport under Phonon Confinement in Nanostructures
• Photon-number dependent afterpulsing in superconducting nanostrip single-photon detectors
• Jitter in photon-number-resolved detection by superconducting nanowires
• Attojoule superconducting thermal logic and memories
• Origin of performance enhancement of superconducting nanowire single-photon detectors by He-ion irradiation