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Author Semenov, A. V.; Devyatov, I. A.; Korneev, A. A.; Smirnov, K. V.; Goltsman, G. N.; Melnikov, A. P.
Title Derivation of expression for thermodynamic potential of “dirty” superconductor Type Journal Article
Year 2012 Publication Rus. J. Radio Electron. Abbreviated Journal Rus. J. Radio Electron.
Volume Issue (down) 4 Pages
Keywords dirty superconductor, Usadel theory, thermodynamic potential
Abstract We derive a formula for thermodynamic potential of dirty superconductor which express it via isotropic quasiclassical Green functions of Usadel theory. Our result allows unify description of dynamic processes and fluctuations in superconducting nano-electronic devices.
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Language Russian Summary Language Original Title
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Notes 7 pages Approved no
Call Number Serial 1824
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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 Sov. Phys. JETP Abbreviated Journal Sov. Phys. JETP
Volume 70 Issue (down) 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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Notes Approved no
Call Number Serial 241
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Author Semenov, A.; Engel, A.; Il'in, K.; Gol'tsman, G.; Siegel, M.; Hübers, H.-W.
Title Ultimate performance of a superconducting quantum detector Type Journal Article
Year 2003 Publication Eur. Phys. J. Appl. Phys. Abbreviated Journal Eur. Phys. J. Appl. Phys.
Volume 21 Issue (down) 3 Pages 171-178
Keywords NbN SSPD, SNSPD
Abstract We analyze the ultimate performance of a superconducting quantum detector in order to meet requirements for applications in near-infrared astronomy and X-ray spectroscopy. The detector exploits a combined detection mechanism, in which avalanche quasiparticle multiplication and the supercurrent jointly produce a voltage response to a single absorbed photon via successive formation of a photon-induced and a current-induced normal hotspot in a narrow superconducting strip. The response time of the detector should increase with the photon energy providing energy resolution. Depending on the superconducting material and operation conditions, the cut-off wavelength for the single-photon detection regime varies from infrared waves to visible light. We simulated the performance of the background-limited infrared direct detector and X-ray photon counter utilizing the above mechanism. Low dark count rate and intrinsic low-frequency cut-off allow for realizing a background limited noise equivalent power of 10−20 W Hz−1/2 for a far-infrared direct detector exposed to 4-K background radiation. At low temperatures, the intrinsic response time of the counter is rather determined by diffusion of nonequilibrium electrons than by the rate of energy transfer to phonons. Therefore, thermal fluctuations do not hamper energy resolution of the X-ray photon counter that should be better than 10−3 for 6-keV photons. Comparison of new data obtained with a Nb based detector and previously reported results on NbN quantum detectors support our estimates of ultimate detector performance.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1286-0042 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 534
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Author Korneeva, Y.; Florya, I.; Semenov, A.; Korneev, A.; Goltsman, G.
Title New generation of nanowire NbN superconducting single-photon detector for mid-infrared Type Journal Article
Year 2011 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume 21 Issue (down) 3 Pages 323-326
Keywords SSPD
Abstract We present a break-through approach to mid-infrared single-photon detection based on nanowire NbN superconducting single-photon detectors (SSPD). Although SSPD became a mature technology for telecom wavelengths (1.3-1.55 μm) its further expansion to mid-infrared wavelength was hampered by low sensitivity above 2 μm. We managed to overcome this limit by reducing the nanowire width to 50 nm, while retaining high superconducting properties and connecting the wires in parallel to produce a voltage response of sufficient magnitude. The new device exhibits 10 times better quantum efficiency at 3.5 μm wavelength than the “standard” SSPD.
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Notes Approved no
Call Number RPLAB @ gujma @ Serial 644
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Author Lobanov, Y.; Shcherbatenko, M.; Finkel, M.; Maslennikov, S.; Semenov, A.; Voronov, B. M.; Rodin, A. V.; Klapwijk, T. M.; Gol'tsman, G. N.
Title NbN hot-electron-bolometer mixer for operation in the near-IR frequency range Type Journal Article
Year 2015 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume 25 Issue (down) 3 Pages 2300704 (1 to 4)
Keywords HEB mixer, IR, optical antenna
Abstract Traditionally, hot-electron-bolometer (HEB) mixers are employed for THz and “super-THz” heterodyne detection. To explore the near-IR spectral range, we propose a fiber-coupled NbN film based HEB mixer. To enhance the incident-light absorption, a quasi-antenna consisting of a set of parallel stripes of gold is used. To study the antenna effect on the mixer performance, we have experimentally studied a set of devices with different size of the Au stripe and spacing between the neighboring stripes. With use of the well-known isotherm technique we have estimated the absorption efficiency of the mixer, and the maximum efficiency has been observed for devices with the smallest pitch of the alternating NbN and NbN-Au stripes. Also, a proper alignment of the incident Eâƒ<2014>-field with respect to the stripes allows us to improve the coupling further. Studying IV-characteristics of the mixer under differently-aligned Eâƒ<2014>-field of the incident radiation, we have noticed a difference in their shape. This observation suggests that a difference exists in the way the two waves with orthogonal polarizations parallel and perpendicular Eâƒ<2014>-field to the stripes heat the electrons in the HEB mixer. The latter results in a variation in the electron temperature distribution over the HEB device irradiated by the two waves.
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Notes Approved no
Call Number Serial 952
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