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Gershenzon, E. M.; Gershenzon, M. E.; Goltsman, G. N.; Lulkin, A.; Semenov, A. D.; Sergeev, A. V. |
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Electron-phonon interaction in ultrathin Nb films |
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1990 |
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Sov. Phys. JETP |
Abbreviated Journal |
Sov. Phys. JETP |
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70 |
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3 |
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505-511 |
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Keywords |
Nb films |
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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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241 |
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Gershenzon, E. M.; Gogidze, I. G.; Goltsman, G. N.; Semenov, A. D.; Sergeev, A. V. |
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Title |
Picosecond response on optical-range emission in thin YBaCuO films |
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Journal Article |
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1991 |
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Pisma v Zhurnal Tekhnicheskoi Fiziki |
Abbreviated Journal |
Pisma v Zhurnal Tekhnicheskoi Fiziki |
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17 |
Issue |
22 |
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6-10 |
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Keywords |
YBCO HTS detectors |
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Целью настоящей работы является целенаправленный поиск пико-секундного отклика на оптическое излучение выяснение оптимальных условий его наблюдения, а также сравнение характеристик неравновесных эффектов в оптическом и субмиллиметровом диапазонах. |
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Russian |
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1684 |
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Sergeev, A. V.; Semenov, A. D.; Kouminov, P.; Trifonov, V.; Goghidze, I. G.; Karasik, B. S.; Gol’tsman, G. N.; Gershenzon, E. M. |
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Title |
Transparency of a YBa2Cu3O7-film/substrate interface for thermal phonons measured by means of voltage response to radiation |
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1994 |
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Phys. Rev. B Condens. Matter. |
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Phys. Rev. B Condens. Matter. |
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49 |
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13 |
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9091-9096 |
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YBCO films |
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The transparency of a film/substrate interface for thermal phonons was investigated for YBa2Cu3O7 thin films deposited on MgO, Al2O3, LaAlO3, NdGaO3, and ZrO2 substrates. Both voltage response to pulsed-visible and to continuously modulated far-infrared radiation show two regimes of heat escape from the film to the substrate. That one dominated by the thermal boundary resistance at the film/substrate interface provides an initial exponential decay of the response. The other one prevailing at longer times or smaller modulation frequencies causes much slower decay and is governed by phonon diffusion in the substrate. The transparency of the boundary for phonons incident from the film on the substrate and also from the substrate on the film was determined separately from the characteristic time of the exponential decay and from the time at which one regime was changed to the other. Taking into account the specific heat of optical phonons and the temperature dependence of the group velocity of acoustic phonons, we show that the body of experimental data agrees with acoustic mismatch theory rather than with the model that assumes strong diffusive scattering of phonons at the interface. |
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0163-1829 |
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PMID:10009690 |
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1648 |
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Gershenzon, E. M.; Gol’tsman, G. N.; Semenov, A. D.; Sergeev, A. V. |
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Title |
Mechanism of picosecond response of granular YBaCuO films to electromagnetic radiation |
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Journal Article |
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1991 |
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IEEE Trans. Magn. |
Abbreviated Journal |
IEEE Trans. Magn. |
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27 |
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2 |
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1321-1324 |
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Keywords |
YBCO HTS detectors |
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Ultrafast mechanisms of radiation detection in granular YBaCuO films are studied in the wide wavelength range from millimeter waves to near infrared. With an increase in 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. The electron-phonon relaxation time tau /sub eph/ is determined from direct measurements, quasi-stationary electron heating measurements, and the frequency dependence of the current at which maximum voltage shift is observed. The temperature dependence of tau /sub eph/ at T<or=40 K was found to be tau /sub eph/ approximately T/sup -1/. The results show that detectors with a response time of a few picoseconds at nitrogen temperature are attainable. |
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1941-0069 |
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1679 |
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Semenov, A. D.; Goghidze, I. G.; Gol’tsman, G. N.; Sergeev, A. V.; Aksaev, E. E.; Gershenzon, E. M. |
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Title |
Non-equilibrium quasiparticle response to radiation and bolometric effect in YBaCuO films |
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Journal Article |
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1993 |
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IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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Volume |
3 |
Issue |
1 |
Pages |
2132-2135 |
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Keywords |
YBCO HTS HEB detectors |
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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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1558-2515 |
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