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Beck, M.; Klammer, M.; Lang, S.; Leiderer, P.; Kabanov, V. V.; Gol'tsman, G. N.; Demsar, J. |
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Title |
Energy-gap dynamics of superconducting NbN thin films studied by time-resolved terahertz spectroscopy |
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Journal Article |
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Year |
2011 |
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Phys. Rev. Lett. |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
107 |
Issue |
17 |
Pages |
4 |
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NbN thin film, energy gap dynamics |
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Using time-domain terahertz spectroscopy we performed direct studies of the photoinduced suppression and recovery of the superconducting gap in a conventional BCS superconductor NbN. Both processes are found to be strongly temperature and excitation density dependent. The analysis of the data with the established phenomenological Rothwarf-Taylor model enabled us to determine the bare quasiparticle recombination rate, the Cooper pair-breaking rate and the electron-phonon coupling constant, λ=1.1±0.1, which is in excellent agreement with theoretical estimates. |
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RPLAB @ gujma @ |
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641 |
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Verevkin, A. A.; Ptitsina, N. G.; Chulcova, G. M.; Gol'Tsman, G. N.; Gershenzon, E. M.; Yngvesson, K. S. |
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Title |
Determination of the limiting mobility of a two-dimensional electron gas in AlxGa1-xAs/GaAs heterostructures and direct measurement of the energy relaxation time |
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Journal Article |
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1996 |
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Phys. Rev. B Condens. Matter. |
Abbreviated Journal |
Phys. Rev. B Condens. Matter. |
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53 |
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12 |
Pages |
R7592-R7595 |
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2DEG, AlGaAs/GaAs heterostructures |
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We present results for a method to measure directly the energy relaxation time (τe) for electrons in a single AlxGa1−xAs/GaAs heterojunction; measurements were performed from 1.6 to 15 K under quasiequilibrium conditions. We find τeαT−1 below 4 K, and τe independent of T above 4 K. We have also measured the energy-loss rate, ⟨Q⟩, by the Shubnikov-de Haas technique, and find ⟨Q⟩α(T3e−T3) for T<~4.2 K; Te is the electron temperature. The values and temperature dependence of τe and ⟨Q⟩ for T<4 K agree with calculations based on piezoelectric and deformation potential acoustic phonon scattering. At 4.2 K, we can also estimate the momentum relaxation time, τm, from our measured τe. This leads to a preliminary estimate of the phonon-limited mobility at 4.2 K of μ=3×107 cm2/Vs (ns=4.2×1011 cm−2), which agrees well with published numerical calculations, as well as with an earlier indirect estimate based on measurements on a sample with much higher mobility. |
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0163-1829 |
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PMID:9982274 |
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1612 |
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Semenov, A. D.; Hübers, H.-W.; Richter, H.; Birk, M.; Krocka, M.; Mair, U.; Smirnov, K.; Gol'tsman, G. N.; Voronov, B. M. |
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Title |
2.5 THz heterodyne receiver with NbN hot-electron-bolometer mixer |
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Journal Article |
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2002 |
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Phys. C: Supercond. |
Abbreviated Journal |
Phys. C: Supercond. |
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372-376 |
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448-453 |
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NbN HEB mixers, applications |
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We describe a 2.5 THz heterodyne receiver for applications in astronomy and atmospheric research. The receiver employs a superconducting NbN phonon-cooled hot-electron-bolometer mixer and an optically pumped far-infrared gas laser as local oscillator. 2200 K double sideband mixer noise temperature was measured at 2.5 THz across a 1 GHz intermediate frequency bandwidth centred at 1.5 GHz. The total conversion losses were 17 dB. The mixer response was linear at load temperatures smaller than 400 K. The receiver was tested in the laboratory environment by measuring the methanol line in emission. Observed pressure broadening confirms the true heterodyne detection regime of the mixer. |
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0921-4534 |
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1526 |
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Gol'tsman, G. N.; Kouminov, P.; Goghidze, I.; Gershenzon, E. M. |
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Title |
Nonequilibrium kinetic inductive response of YBaCuO thin films to low-power laser pulses |
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Journal Article |
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Year |
1994 |
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Phys. C: Supercond. |
Abbreviated Journal |
Phys. C: Supercond. |
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235-240 |
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1979-1980 |
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YBCO HTS KID |
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Transient non-equilibrium kinetic inductive voltage response of YBaCuO thin films to 20 ps pulses of YAG:Nd laser radiation with 0.63 μm and 1.5 μm wavelength has been revealed. By increasing the sensitivity of 100 ps resolution time registration system and diminishing light intensity (fluence 0.1-1 μJ2/cm2) and transport current (density j≤105 A/cm2) we observed a perculiar bipolar signal form with nearly equal amplitudes of each sign. The integration of the kinetic inductive response over time gives the result which is qualitatively of the same form as the response in the resistive and normal states: nonequilibrium picosecond scale component followed by bolometric nanosecond. Nonequilibrium response is interpreted as suppression of order parameter by excess of quasiparticles followed by a change in resistance in the resistive state and kinetic inductance in superconductive state. |
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0921-4534 |
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1634 |
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Gershenzon, E. M.; Gol'tsman, G. N.; Gogidze, I. G.; Semenov, A. D.; Sergeev, A. V. |
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Processes of electron-phonon interaction in thin YBaCuO films |
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Journal Article |
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1991 |
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Phys. C: Supercond. |
Abbreviated Journal |
Phys. C: Supercond. |
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185-189 |
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1371-1372 |
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Keywords |
YBCO HTS detectors |
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The ultrafast voltage response of YBaCuO films to laser radiation is studied and compared with previously investigated quasiparicles response to radiation of submillimeter wavelength range. Voltage shift under the visible light radiation has two components. Picosecond response realized as suppression superconductivity by nonequilibrium excess quasiparticles, response time is determined by quasiparticles recombination rate. Nanosecond response is probably due to bolometric effect. |
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0921-4534 |
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1676 |
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Gousev, Y. P.; Semenov, A. D.; Gol'tsman, G. N.; Sergeev, A. V.; Gershenzon, E. M. |
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Electron-phonon interaction in disordered NbN films |
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Journal Article |
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1994 |
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Phys. B Condens. Mat. |
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Phys. B Condens. Mat. |
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194-196 |
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1355-1356 |
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NbN films |
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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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0921-4526 |
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1649 |
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Gershenzon, E. M.; Gol'tsman, G. N.; Potapov, V. D.; Sergeev, A. V. |
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Restriction of microwave enhancement of superconductivity in impure superconductors due to electron-electron interaction |
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Journal Article |
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1991 |
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Phys. B Condens. Mat. |
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Phys. B Condens. Mat. |
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169 |
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1-4 |
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629-630 |
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impure superconductors |
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Transition from microwave enhancement of supercurrent to superconductivity suppression is investigated in impure superconductors. It is demonstrated that frequency range of enhancement effect narrows with the decrease of electron mean free path, ℓ, and at ℓ⩽1nm electron heating is observed in the whole frequency range. Dependences of frequency boundaries on ℓ are explained by taking into account strong electron-electron interaction in impure metals. |
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0921-4526 |
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1682 |
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Varyukhin, S. V.; Zakharov, A. A.; Gershenzon, E. M.; Gol'tsman, G. N.; Ptitsyna, N. G.; Chulkova, G. M. |
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AC losses and submillimeter absorption in single crystals La2CuO4 |
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Journal Article |
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1990 |
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Phys. B Condens. Mat. |
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Phys. B Condens. Mat. |
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165-166 |
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1269-1270 |
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metal-dielectric-La2Cu04 |
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The La2CuO4 single crystals were used to carry out the measurements of transmission spectra within the submillimeter range of wavelengths, as well as the capacitance C and conductivity G in the region of acoustic frequencies of the metal-dielectric-La2Cu04 system at low temperatures. The optical spectra display a threshold character. There takes place a sharp decreasing of transmission signal in the energy range of hυ>1.5meV. The C(ω,T) and G(ω,T) dependences have a universal form characteristic of relaxation processes of the Debye type. The relaxation time dependence displays a thermoactivation character τ(T)-exp(ξ/T) with a gap value of ξ≃2meV,coinciding with the optical one. It is assumed that there exist excitations with a characteristic energy ~ 2meV in La2Cu04.A possible nature of the revealed low-energy excitations is discussed. |
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0921-4526 |
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1686 |
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Morozov, P.; Lukina, M.; Shirmanova, M.; Divochiy, A.; Dudenkova, V.; Gol'tsman, G. N.; Becker, W.; Shcheslavskiy, V. I. |
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Singlet oxygen phosphorescence imaging by superconducting single-photon detector and time-correlated single-photon counting |
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Journal Article |
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2021 |
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Opt. Lett. |
Abbreviated Journal |
Opt. Lett. |
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46 |
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6 |
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1217-1220 |
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SSPD, SNSPD, applications |
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This Letter presents, to the best of our knowledge, a novel optical configuration for direct time-resolved measurements of luminescence from singlet oxygen, both in solutions and from cultured cells on photodynamic therapy. The system is based on the superconducting single-photon detector, coupled to the confocal scanner that is modified for the near-infrared measurements. The recording of a phosphorescence signal from singlet oxygen at 1270 nm has been done using time-correlated single-photon counting. The performance of the system is verified by measuring phosphorescence from singlet oxygen generated by the photosensitizers commonly used in photodynamic therapy: methylene blue and chlorin e6. The described system can be easily upgraded to the configuration when both phosphorescence from singlet oxygen and fluorescence from the cells can be detected in the imaging mode. Thus, co-localization of the signal from singlet oxygen with the areas inside the cells can be done. |
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0146-9592 |
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PMID:33720151 |
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1221 |
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Nebosis, R. S.; Heusinger, M. A.; Semenov, A. D.; Lang, P. T.; Schatz, W.; Steinke, R.; Renk, K. F.; Gol'tsman, G. N.; Karasik, B. S.; Gershenzon, E. M. |
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Ultrafast photoresponse of an YBa2Cu3O7-δ film to far-infrared radiation pulses |
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Journal Article |
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1993 |
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Opt. Lett. |
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Opt. Lett. |
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18 |
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2 |
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96-97 |
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YBCO HTS detectors |
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We report the observation of an ultrafast photoresponse of a high-T(c), film to far-infrared radiation pulses. The response of a sample, consisting of a current-carrying structured YBa(2)Cu(3)O(7-delta) film cooled to liquid-nitrogen temperature, was studied by use of ultrashort laser pulses from an optically pumped far-infrared laser in the frequency range from 0.7 to 7 THz. We found that the response time was limited by the time resolution, 120 ps, of our electronic registration equipment. |
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0146-9592 |
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PMID:19802049 |
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1660 |
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