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Author Sidorova, M.; Semenov, Alexej D.; Hübers, H.-W.; Ilin, K.; Siegel, M.; Charaev, I.; Moshkova, M.; Kaurova, N.; Goltsman, G. N.; Zhang, X.; Schilling, A.
Title Electron energy relaxation in disordered superconducting NbN films Type Journal Article
Year (up) 2020 Publication Phys. Rev. B Abbreviated Journal Phys. Rev. B
Volume 102 Issue 5 Pages 054501 (1 to 15)
Keywords NbN SSPD, SNSPD, HEB, bandwidth, relaxation time
Abstract We report on the inelastic-scattering rate of electrons on phonons and relaxation of electron energy studied by means of magnetoconductance, and photoresponse, respectively, in a series of strongly disordered superconducting NbN films. The studied films with thicknesses in the range from 3 to 33 nm are characterized by different Ioffe-Regel parameters but an almost constant product qTl (qT is the wave vector of thermal phonons and l is the elastic mean free path of electrons). In the temperature range 14–30 K, the electron-phonon scattering rates obey temperature dependencies close to the power law 1/τe−ph∼Tn with the exponents n≈3.2–3.8. We found that in this temperature range τe−ph and n of studied films vary weakly with the thickness and square resistance. At 10 K electron-phonon scattering times are in the range 11.9–17.5 ps. The data extracted from magnetoconductance measurements were used to describe the experimental photoresponse with the two-temperature model. For thick films, the photoresponse is reasonably well described without fitting parameters, however, for thinner films, the fit requires a smaller heat capacity of phonons. We attribute this finding to the reduced density of phonon states in thin films at low temperatures. We also show that the estimated Debye temperature in the studied NbN films is noticeably smaller than in bulk material.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2469-9950 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 1266
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Author Ovchinnikov, O. V.; Perepelitsa, A. S.; Smirnov, M. S.; Latyshev, A. N.; Grevtseva, I. G.; Vasiliev, R. B.; Goltsman, G. N.; Vitukhnovsky, A. G.
Title Luminescence of colloidal Ag2S/ZnS core/shell quantum dots capped with thioglycolic acid Type Journal Article
Year (up) 2020 Publication J. Luminescence Abbreviated Journal J. Luminescence
Volume 220 Issue Pages 117008 (1 to 7)
Keywords Ag2S QD, quantum dots
Abstract The features of IR luminescence of colloidal AgS QDs passivated with thioglycolic acid (AgS/TGA) under the formation of AgS/ZnS/TGA core/shell QDs are considered. A 4.5-fold increase in the quantum yield of recombination IR luminescence within the band with a peak at 960 nm (1.29 eV), full width at half maximum of 250 nm (0.34 eV), and the Stokes shift with respect to the exciton absorption of 0.6 eV was found. The increase in the IR luminescence intensity of AgS/ZnS/TGA QDs is accompanied by an increase in the average luminescence lifetime from 2.9 ns to 14.3 ns, which is explained as “healing” of surface trap states during the formation of the ZnS shell. For the first time, the enhancement of the luminescence intensity photodegradation (hereinafter referred to as fatigue) was found during the formation of the AgS/ZnS/TGA core/shell QDs. The luminescence fatigue is irreversible. We conclude that the initial stage of photolysis of the AgS core QDs under laser irradiation plays a key role. Low-atomic photolytic clusters of silver formed on the AgS core QDs act as luminescence quenching centers and do not reveal structural transformations into AgS, provided that the clusters are not in contact with TGA.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0022-2313 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 1267
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Author Shcherbatenko, M. L.; Elezov, M. S.; Goltsman, G. N.; Sych, D. V.
Title Sub-shot-noise-limited fiber-optic quantum receiver Type Journal Article
Year (up) 2020 Publication Phys. Rev. A Abbreviated Journal Phys. Rev. A
Volume 101 Issue 3 Pages 032306 (1 to 5)
Keywords SSPD mixer, SNSPD
Abstract We experimentally demonstrate a quantum receiver based on the Kennedy scheme for discrimination between two phase-modulated weak coherent states. The receiver is assembled entirely from standard fiber-optic elements and operates at a conventional telecom wavelength of 1.55 μm. The local oscillator and the signal are transmitted through different optical fibers, and the displaced signal is measured with a high-efficiency superconducting nanowire single-photon detector. We show the discrimination error rate is two times below that of a shot-noise-limited receiver with the same system detection efficiency.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2469-9926 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 1268
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Author Baeva, E. M.; Titova, N. A.; Veyrat, L.; Sacépé, B.; Semenov, A. V.; Goltsman, G. N.; Kardakova, A. I.; Khrapai, V. S.
Title Thermal relaxation in metal films bottlenecked by diffuson lattice excitations of amorphous substrates Type Miscellaneous
Year (up) 2021 Publication arXiv Abbreviated Journal arXiv
Volume Issue Pages
Keywords metal films, NbN, InOx, Au/Ni, thermal relaxation
Abstract Here we examine the role of the amorphous insulating substrate in the thermal relaxation in thin NbN, InOx, and Au/Ni films at temperatures above 5 K. The studied samples are made up of metal bridges on an amorphous insulating layer lying on or suspended above a crystalline substrate. Noise thermometry was used to measure the electron temperature Te of the films as a function of Joule power per unit of area P2D. In all samples, we observe the dependence P2D∝Tne with the exponent n≃2, which is inconsistent with both electron-phonon coupling and Kapitza thermal resistance. In suspended samples, the functional dependence of P2D(Te) on the length of the amorphous insulating layer is consistent with the linear T-dependence of the thermal conductivity, which is related to lattice excitations (diffusons) for the phonon mean free path smaller than the dominant phonon wavelength. Our findings are important for understanding the operation of devices embedded in amorphous dielectrics.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 1163
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Author Zolotov, P. I.; Semenov, A. V.; Divochiy, A. V.; Goltsman, G. N.; Romanov, N. R.; Klapwijk, T. M.
Title Dependence of photon detection efficiency on normal-state sheet resistance in marginally superconducting films of NbN Type Journal Article
Year (up) 2021 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume 31 Issue 5 Pages 1-5
Keywords NbN SSPD, SNSPD
Abstract We present an extensive set of data on nanowire-type superconducting single-photon detectors based on niobium-nitride (NbN) to establish the empirical correlation between performance and the normal-state resistance per square. We focus, in particular, on the bias current, compared to the expected depairing current, needed to achieve a near-unity detection efficiency for photon detection. The data are discussed within the context of a model in which the photon energy triggers the movement of vortices i.e. superconducting dissipation, followed by thermal runaway. Since the model is based on the non-equilibrium theory for conventional superconductors deviations may occur, because the efficient regime is found when NbN acts as a marginal superconductor in which long-range phase coherence is frustrated.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1051-8223 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 1222
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