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Author Gershenzon, E. M.; Gershenzon, M. E.; Goltsman, G. N.; Lulkin, A.; Semenov, A. D.; Sergeev, A. V.
Title Electron-phonon interaction in ultrathin Nb films Type Journal Article
Year 1990 Publication (down) Sov. Phys. JETP Abbreviated Journal Sov. Phys. JETP
Volume 70 Issue 3 Pages 505-511
Keywords Nb films
Abstract A study was made of the heating of electrons in normal resistive states of superconducting thin Nb films. The directly determined relaxation time of the resistance of a sample and the rise of the electron temperature were used to find the electron-phonon interaction time rep,, The dependence of rep, on the mean free path of electrons re,, a 1-'demonstrated, in agreement with the theoretical predictions, that the contribution of the inelastic scattering of electrons by impurities to the energy relaxation process decreased at low temperatures and the observed temperature dependence rep, a T 2 was due to a modification of the phonon spectrum in thin fllms.

1. Much new information on the electron-phonon interaction time?;,, in thin films of normal metals and superconductors has been published recently. This information has been obtained mainly as a result of two types of measurement. One includes experiments on weak electron localization investigated by the method of quantum interference corrections to the conductivity of disordered conductors, which can be used to find the relaxation time T, of the phase of the electron wave function. In the absence of the scattering of electrons by paramagnetic impurities the relaxation time T, is associated with the most effective process of energy relaxation: T;= TL+ rep;, where T,, is the electronelectron relaxation time. At low temperatures, when the dependence T; a T is exhibited by thin disordered films, the dominant channel is that of the electron-electron relaxation and there is a lower limit to the temperature range in which rep, can be investigated.
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Call Number Serial 241
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Author Gershenzon, E. M.; Gershenzon, M. E.; Gol'tsman, G. N.; Semenov, A. D.; Sergeev, A. V.
Title Heating of electrons in a superconductor in the resistive state by electromagnetic radiation Type Journal Article
Year 1984 Publication (down) Sov. Phys. JETP Abbreviated Journal Sov. Phys. JETP
Volume 59 Issue 2 Pages 442-450
Keywords Nb HEB
Abstract The effect of heating of electrons relative to phonons is observed and investigated in a superconducting film that is made resistive by current and by an external magnetic field. The effect is manifested by an increase of the film resistance under the influence of the electromagnetic radiation, and is not selective in the frequency band 10^10-10^15 Hz. The independence of the effect of frequency under conditions of strong scattering by static defects is attributed to the decisive role of electron-electron collisions in the distribution function. The experimentally obtained characteristic time of resistance variation near the superconducting transition corresponds to the relaxation time of the order parameter, while at lower temperatures and fields it corresponds to the time of the inelastic electron-phonon interaction.
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Call Number RPLAB @ phisix @ Serial 983
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Author Bespalov, A.V.; Gol'tsman, G.N.; Semenov, A.D.; Renk, K.F.
Title Determination of the far-infrared emission characteristic of a cyclotron p-germanium laser by use of a superconducting Nb detector Type Journal Article
Year 1991 Publication (down) Solid State Communications Abbreviated Journal Solid State Communications
Volume 80 Issue 7 Pages 503-506
Keywords Nb detector, applications
Abstract We studied the far-infrared emission characteristics of a cyclotron p-germanium laser using a broad-band superconducting Nb film detector. For magnetic fields between ∼25 kOe and ∼50 kOe, emission in a frequency range from ∼50 cm-1 to ∼100 cm-1 with maximum intensity around 90 cm-1 was obtained. We determined, for fixed magnetic fields, electric field dependences of the emission intensity taking into account that the total electric field is a sum of the applied and the Hall electric field. An analysis of the emission intensity characteristic gives evidence that transitions between the two lowest Landau levels of light holes are responsible for the laser action.
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ISSN 0038-1098 ISBN Medium
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Notes Approved no
Call Number Serial 1677
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Author Gershenzon, E. M.; Gol'tsman, G. N.; Semenov, A. D.; Sergeev, A. V.
Title Mechanism of picosecond response of granular YBaCuO films to electromagnetic radiation Type Journal Article
Year 1990 Publication (down) Solid State Communications Abbreviated Journal Solid State Communications
Volume 76 Issue 4 Pages 493-497
Keywords YBCO HTS detectors
Abstract The ultrafast mechanisms of radiation detection in granular YBaCuO films are studied in the wide wavelength range from millimeter to near infrared. With the rise of radiation frequency the Josephson detection at the grain boundary weak links is replaced by electron heating into the grains. This change occurs in the submillimeter wavelength range. Electron-phonon relaxation time τeph is determined by direct measurements and analyses quasistationary electron heating. Temperature dependence of τeph at T ≤ 40 K was found to be τeph ∼ T−1. The results show that detectors with the response time of few picoseconds at nitrogen temperature are attainable.
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ISSN 0038-1098 ISBN Medium
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Notes Approved no
Call Number Serial 1685
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Author Murphy, A.; Semenov, A.; Korneev, A.; Korneeva, Y.; Gol'tsman, G.; Bezryadin, A.
Title Three temperature regimes in superconducting photon detectors: quantum, thermal and multiple phase-slips as generators of dark counts Type Journal Article
Year 2015 Publication (down) Sci. Rep. Abbreviated Journal Sci. Rep.
Volume 5 Issue Pages 10174 (1 to 10)
Keywords SPD, SSPD, SNSPD
Abstract We perform measurements of the switching current distributions of three w approximately 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter of the vortex cores, so they are classified as quasi-two-dimensional (quasi-2D). We discover evidence of macroscopic quantum tunneling by observing the saturation of the standard deviation of the switching distributions at temperatures around 2 K. We analyze our results using the Kurkijarvi-Garg model and find that the escape temperature also saturates at low temperatures, confirming that at sufficiently low temperatures, macroscopic quantum tunneling is possible in quasi-2D strips and can contribute to dark counts observed in single photon detectors. At the highest temperatures the system enters a multiple phase-slip regime. In this range single phase-slips are unable to produce dark counts and the fluctuations in the switching current are reduced.
Address Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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ISSN 2045-2322 ISBN Medium
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Notes PMID:25988591; PMCID:PMC4437302 Approved no
Call Number Serial 1344
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