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Author Arutyunov, K. Y.; Ramos-Álvarez, A.; Semenov, A. V.; Korneeva, Y. P.; An, P. P.; Korneev, A. A.; Murphy, A.; Bezryadin, A.; Gol’tsman, G. N. url  openurl
  Title Quasi-1-dimensional superconductivity in highly disordered NbN nanowires Type Miscellaneous
  Year 2016 Publication arXiv Abbreviated Journal  
  Volume Issue Pages (up)  
  Keywords narrow NbN nanowires, BCS  
  Abstract The topic of superconductivity in strongly disordered materials has attracted a significant attention. In particular vivid debates are related to the subject of intrinsic spatial inhomogeneity responsible for non-BCS relation between the superconducting gap and the pairing potential. Here we report experimental study of electron transport properties of narrow NbN nanowires with effective cross sections of the order of the debated inhomogeneity scales. We find that conventional models based on phase slip concept provide reasonable fits for the shape of the R(T) transition curve. Temperature dependence of the critical current follows the text-book Ginzburg-Landau prediction for quasi-one-dimensional superconducting channel Ic~(1-T/Tc)^3/2. Hence, one may conclude that the intrinsic electronic inhomogeneity either does not exist in our structures, or, if exist, does not affect their resistive state properties.  
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  Notes Duplicated as 1332 Approved no  
  Call Number Serial 1338  
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Author Sidorova, M.; Semenov, A.; Korneev, A.; Chulkova, G.; Korneeva, Y.; Mikhailov, M.; Devizenko, A.; Kozorezov, A.; Goltsman, G. url  openurl
  Title Electron-phonon relaxation time in ultrathin tungsten silicon film Type Miscellaneous
  Year 2018 Publication arXiv Abbreviated Journal  
  Volume Issue Pages (up)  
  Keywords WSi film  
  Abstract Using amplitude-modulated absorption of sub-THz radiation (AMAR) method, we studied electron-phonon relaxation in thin disordered films of tungsten silicide. We found a response time ~ 800 ps at critical temperature Tc = 3.4 K, which scales as minus 3 in the temperature range from 1.8 to 3.4 K. We discuss mechanisms, which can result in a strong phonon bottle-neck effect in a few nanometers thick film and yield a substantial difference between the measured time, characterizing response at modulation frequency, and the inelastic electron-phonon relaxation time. We estimate the electron-phonon relaxation time to be in the range ~ 100-200 ps at 3.4 K.  
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  Notes Duplicated as 1341 Approved no  
  Call Number Serial 1340  
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Author Sidorova, M. V.; Kozorezov, A. G.; Semenov, A. V.; Korneev, A. A.; Chulkova, G. M.; Korneeva, Y. P.; Mikhailov, M. Y.; Devizenko, A. Y.; Goltsman, G. N. url  openurl
  Title Non-bolometric bottleneck in electron-phonon relaxation in ultra-thin WSi film Type Miscellaneous
  Year 2018 Publication arXiv Abbreviated Journal  
  Volume Issue Pages (up)  
  Keywords WSi films, diffusion constant, SSPD, SNSPD  
  Abstract We developed the model of the internal phonon bottleneck to describe the energy exchange between the acoustically soft ultrathin metal film and acoustically rigid substrate. Discriminating phonons in the film into two groups, escaping and nonescaping, we show that electrons and nonescaping phonons may form a unified subsystem, which is cooled down only due to interactions with escaping phonons, either due to direct phonon conversion or indirect sequential interaction with an electronic system. Using an amplitude-modulated absorption of the sub-THz radiation technique, we studied electron-phonon relaxation in ultrathin disordered films of tungsten silicide. We found an experimental proof of the internal phonon bottleneck. The experiment and simulation based on the proposed model agree well, resulting in tau{e-ph} = 140-190 ps at TC = 3.4 K, supporting the results of earlier measurements by independent techniques.  
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  Notes Duplicated as 1305 Approved no  
  Call Number Serial 1341  
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Author Murphy, A.; Semenov, A.; Korneev, A.; Korneeva, Y.; Gol’tsman, G.; Bezryadin, A. url  openurl
  Title Dark counts initiated by macroscopic quantum tunneling in NbN superconducting photon detectors Type Miscellaneous
  Year 2014 Publication arXiv Abbreviated Journal  
  Volume Issue Pages (up)  
  Keywords NbN SSPD  
  Abstract We perform measurements of the switching current distributions of three w = 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter 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.  
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  Call Number murphy2014dark Serial 1356  
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Author Pernice, W.; Schuck, C.; Li, M.; Goltsman, G. N.; Sergienko, A. V.; Tang, H. X. openurl 
  Title High speed travelling wave single-photon detectors with near-unity quantum efficiency Type Journal Article
  Year 2011 Publication arXiv Abbreviated Journal arXiv  
  Volume Issue Pages (up) 1-14  
  Keywords SPD  
  Abstract Ultrafast, high quantum efficiency single photon detectors are among the most sought-after elements in modern quantum optics and quantum communication. Close-to-unity photon detection efficiency is essential for scalable measurement-based quantum computation, quantum key distribution, and loophole-free Bell experiments. However, imperfect modal matching and finite photon absorption rates have usually limited the maximum attainable detection efficiency of single photon detectors. Here we demonstrate a superconducting nanowire detector atop nanophotonic waveguides and achieve single photon detection efficiency up to 94% at telecom wavelengths. Our detectors are fully embedded in a scalable, low loss silicon photonic circuit and provide ultrashort timing jitter of 18ps at multi-GHz detection rates. Exploiting this high temporal resolution we demonstrate ballistic photon transport in silicon ring resonators. The direct implementation of such a detector with high quantum efficiency, high detection speed and low jitter time on chip overcomes a major barrier in integrated quantum photonics.  
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  Publisher Place of Publication arXiv:1108.5299 Editor  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 661  
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