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Men’shchikov EM, Gogidze IG, Sergeev AV, Elant’ev AI, Kuminov PB, Gol’tsman GN, et al. Superconducting fast detector based on the nonequilibrium inductance response of a film of niobium nitride. Tech Phys Lett. 1997;23(6):486–8.
Abstract: A new type of fast detector is proposed, whose operation is based on the variation of the kinetic inductance of a superconducting film caused by nonequilibrium quasiparticles created by the electromagnetic radiation. The speed of the detector is determined by the rate of multiplication of photo-excited quasiparticles, and is nearly independent of the temperature, being less than 1 ps for NbN. Models based on the Owen-Scalapino scheme give a good description of the experimentally determined dependence of the power-voltage sensitivity of the detector on the modulation frequency. The lifetime of the quasiparticles is determined, and it is shown that the reabsorption of nonequilibrium phonons by the condensate has a substantial effect even in ultrathin NbN films 5 nm thick, and results in the maximum possible quantum yield. A low concentration of equilibrium quasiparticles and a high quantum yield result in a detectivity D*=1012 W−1·Hz1/2 at a temperature T=4.2 K and D*=1016 W−1·cm· Hz1/2 at T=1.6 K.
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Semenov AD, Heusinger MA, Renk KF, Menschikov E, Sergeev AV, Elant'ev AI, et al. Influence of phonon trapping on the performance of NbN kinetic inductance detectors. IEEE Trans Appl Supercond. 1997;7(2):3083–6.
Abstract: Voltage and microwave photoresponse of NbN thin films to modulated and pulsed optical radiation reveals, far below the superconducting transition, a response time consistent with the lifetime of nonequilibrium quasiparticles. We show that even in 5 nm thick films at 4.2 K the phonon trapping is significant resulting in a quasiparticle lifetime of a few nanoseconds that is an order of magnitude larger than the recombination time. Values and temperature dependence of the quasiparticle lifetime obey the Bardeen-Cooper-Schrieffer theory and are in quantitative agreement with the electron-phonon relaxation rate determined from the resistive response near the superconducting transition. We discuss a positive effect of the phonon trapping on the performance of kinetic inductance detectors.
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Il'in KS, Karasik BS, Ptitsina NG, Sergeev AV, Gol'tsman GN, Gershenzon EM, et al. Electron-phonon-impurity interference in thin NbC films: electron inelastic scattering time and corrections to resistivity. In: Czech. J. Phys. Vol 46.; 1996. p. 857–8.
Abstract: Complex study of transport properties of impure NbC films with the electron mean free pathl=0.6–13 nm show the crucial role of the electron-phonon-impurity interference (EPII). In the temperature range 20–70 K we found the interference correction to resistivity proportional to T2 and to the residual resistivity of the film. Using the comprehensive theory of EPII, we determine the electron coupling with transverse phonons and calculate the electron inelastic scattering time. Direct measurements of the inelastic electron scattering time using a response to a high-frequency amplitude modulated cw radiation agree well with the theory.
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Gousev YP, Semenov AD, Gol'tsman GN, Sergeev AV, Gershenzon EM. Electron-phonon interaction in disordered NbN films. Phys B Condens Mat. 1994;194-196:1355–6.
Abstract: Electron-phonon interaction time has been investigated in disordered films of NbN. A temperatures below 5.5 K tau_eph ~ T -1"6 which is attributed to the renormalisation of phonon spectrum in thin films.
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Semenov AD, Goghidze IG, Gol’tsman GN, Sergeev AV, Gershenzon EM. Evidence for the spectral dependence of nonequilibrium picosecond photoresponse of YBaCuO thin films. Appl Phys Lett. 1993;63(5):681–3.
Abstract: The transient voltage photoresponse of current biased YBaCuO thin films to 20 ps laser pulses of 0.63 and 1.54 μm wavelengths is measured for temperatures around the superconducting transition region. The fast picosecond decay of the response is followed by a slow nanosecond relaxation which is associated with the bolometric effect. The magnitude of the fast component of the response varies in proportion to the square root of wavelength that plausibly reflects multiplication processes of photoexcited electrons via electron–electron scattering and interaction with high energy phonons.
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Semenov AD, Goghidze IG, Gol’tsman GN, Sergeev AV, Aksaev EE, Gershenzon EM. Non-equilibrium quasiparticle response to radiation and bolometric effect in YBaCuO films. IEEE Trans Appl Supercond. 1993;3(1):2132–5.
Abstract: The voltage photoresponse of structured current biased YBCO films on different substrates to 20-ps laser pulses of 0.63- mu m and 1.54- mu m wavelengths and to continuously modulated radiation of 2-mm wavelength is measured to temperatures around Tc. Fast picosecond decay of the response to pulsed radiation is followed by slow exponential relaxation with a nanosecond characteristic time depending on the substrate material and film dimensions. The slow component does not depend on wavelength and is attributed to the bolometric effect, while the magnitude of the fast component associated with nonequilibrium response rises with wavelength. More than an order-of-magnitude increase of the nonequilibrium response is seen from near-infrared to millimeter-wave range. This dependence plausibly reflects the low efficiency of multiplication of photoexcited electrons in YBaCuO compared to conventional superconductors.
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Semenov AD, Sergeev AV, Kouminov P, Goghidze IG, Heusinger MA, Nebosis RS, et al. Transparency of YBCO film/substrate interfaces for thermal phonons determined by photoresponse measurements. In: Freyhardt HC, editor. Proc. 1st European Conf. on Appl. Supercond. Vol 2.; 1993. p. 1443–6.
Abstract: Direct measurements of the thermal boundary resistance were performed by means of the stationary method. In this approach the temperature of an electrically heated film is controlled by its dc resistance while an additional film on the same substrate is used as a thermometer monitoring substrate temperature. The temperature field in the substrate is then calculated to deduce the Kapitza temperature step at the interface between the heated strip and the substrate. The main statement of all afore-said papers is that experimental values of the thermal boundary resistance are too large to be explained by the acoustic mismatch model. In this paper we investigate transparency of YBaCuO film/substrate interfaces for thermal phonons by means of photoresponse measurements. We show that our data are in reasonable agreement with the acoustic mismatch theory.
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Gol’tsman GN, Semenov AD, Sergeev AV, Aksaev EE, Gogidze IG, Gershenzon EM. Electron-phonon interaction in thin YBaCuO films and fast detectors. In: Meissner M, Pohl RO, editors. Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences. Vol 112.; 1993. p. 184–5.
Abstract: The thin. YBaCuO film response to laser and submillimeter radiation demonstrates the picosecond nonequilibrium peak on the nanosecond bolometric background. Experimental data give an evidence for the spectral dependence of picosecond photoresponse probably due to a poor efficiency of electron multiplication processes. Presented results prove an availability of fast YBaCuO thin film detector.
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Sergeev AV, Livanov DV. Phonon renormalization of thermoelectric power of high-Tc materials. In: Meissner M, Pohl RO, editors. Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences. Vol 112.; 1993. p. 204–5.
Abstract: Renormalization of thermoelectric power due to Nielsen — Taylor effect (interference between electron-phonon and electron- impurity interactions) is used for the explanation of the temperature dependence and sign of the thermopower in high-Tc materials. In the framework of the model the negative sign of TEP of untwinned YBa2Cu3O7−x crystal in a-direction observed by Howson et. al. is connected to the strong hole scattering via O-vacancies in chains.
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Sergeev AV, Aksaev EE, Gogidze IG, Gol’tsman GN, Semenov AD, Gershenzon EM. Thermal boundary resistance at YBaCuO film-substrate interface. In: Meissner M, Pohl RO, editors. Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences. Vol 112.; 1993. p. 405–6.
Abstract: The nanosecond voltage response of YBaCuo films on Al2O3, MgO and ZrO2 substrates to electromagnetic radiation of millimeter and visible ranges has been investigated. The analysis of experimental conditions for Al2O3 and MgO substrates shows that the resistance change is monitored by the Kapitza boundary shift of temperature during the temporal interval ~ 100 ns limited by the time of phonon return from a substrate into a film. The observed exponential voltage decay is described by the phonon escape time which is proportional to the film thickness and is weakly temperature dependent.
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