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Author |
Vercruyssen, N.; Verhagen, T. G. A.; Flokstra, M. G.; Pekola, J. P.; Klapwijk, T. M. |
Title |
Evanescent states and nonequilibrium in driven superconducting nanowires |
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Journal Article |
Year |
2012 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume ![sorted by Volume (numeric) field, ascending order (up)](img/sort_asc.gif) |
85 |
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224503(1-10) |
Keywords |
Al HEB, Al superconducting nanowire, global state, bimodal state, quasiclassical kinetic equations, Usadel equation |
Abstract |
We study the nonlinear response of current transport in a superconducting diffusive nanowire between normal reservoirs. We demonstrate theoretically and experimentally the existence of two different superconducting states appearing when the wire is driven out of equilibrium by an applied bias, called the global and bimodal superconducting states. The different states are identified by using two-probe measurements of the wire, and measurements of the local density of states with tunneling probes. The analysis is performed within the framework of the quasiclassical kinetic equations for diffusive superconductors. |
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898 |
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Peltonen, J. T.; Astafiev, O. V.; Korneeva, Y. P.; Voronov, B. M.; Korneev, A. A.; Charaev, I. M.; Semenov, A. V.; Golt'sman, G. N.; Ioffe, L. B.; Klapwijk, T. M.; Tsai, J. S. |
Title |
Coherent flux tunneling through NbN nanowires |
Type |
Journal Article |
Year |
2013 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume ![sorted by Volume (numeric) field, ascending order (up)](img/sort_asc.gif) |
88 |
Issue |
22 |
Pages |
220506 (1 to 5) |
Keywords |
NbN nanowires |
Abstract |
We demonstrate evidence of coherent magnetic flux tunneling through superconducting nanowires patterned in a thin highly disordered NbN film. The phenomenon is revealed as a superposition of flux states in a fully metallic superconducting loop with the nanowire acting as an effective tunnel barrier for the magnetic flux, and reproducibly observed in different wires. The flux superposition achieved in the fully metallic NbN rings proves the universality of the phenomenon previously reported for InOx. We perform microwave spectroscopy and study the tunneling amplitude as a function of the wire width, compare the experimental results with theories, and estimate the parameters for existing theoretical models. |
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1098-0121 |
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1369 |
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Lusche, R.; Semenov, A.; Korneeva, Y.; Trifonov, A.; Korneev, A.; Gol'tsman, G.; Hübers, H.-W. |
Title |
Effect of magnetic field on the photon detection in thin superconducting meander structures |
Type |
Journal Article |
Year |
2014 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume ![sorted by Volume (numeric) field, ascending order (up)](img/sort_asc.gif) |
89 |
Issue |
10 |
Pages |
104513 (1 to 7) |
Keywords |
NbN SSPD, SNSPD |
Abstract |
We have studied the influence of an externally applied magnetic field on the photon and dark count rates of meander-type niobium nitride superconducting nanowire single-photon detectors. Measurements have been performed at a temperature of 4.2 K, and magnetic fields up to 250 mT have been applied perpendicularly to the meander plane. While photon count rates are field independent at weak applied fields, they show a strong dependence at fields starting from approximately ±25 mT. This behavior, as well as the magnetic field dependence of the dark count rates, is in good agreement with the recent theoretical model of vortex-assisted photon detection and spontaneous vortex crossing in narrow superconducting lines. However, the local reduction of the superconducting free energy due to photon absorption, which is the fitting parameter in the model, increases much slower with the photon energy than the model predicts. Furthermore, changes in the free-energy during photon counts and dark counts depend differently on the current that flows through the meander. This indicates that photon counts and dark counts occur in different parts of the meander. |
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1367 |
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Kozorezov, A. G.; Lambert, C.; Marsili, F.; Stevens, M. J.; Verma, V. B.; Stern, J. A.; Horansky, R.; Dyer, S.; Duff, S.; Pappas, D. P.; Lita, A.; Shaw, M. D.; Mirin, R. P.; Sae Woo Nam |
Title |
Quasiparticle recombination in hotspots in superconducting current-carrying nanowires |
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Journal Article |
Year |
2015 |
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Phys. Rev. B |
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92 |
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6 |
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We describe a kinetic model of recombination of non-equilibrium quasiparticles generated by single photon absorption in superconducting current-carrying nanowires. The model is developed to interpret two-photon detection experiments in which a single photon does not possess sufficient energy for breaking superconductivity at a fixed low bias current. We show that quasiparticle self- recombination in relaxing hotspot dominates diffusion expansion effects and explains the observed strong bias current, wavelength and temperature dependencies of hotspot relaxation in tungsten silicide superconducting nanowire single-photon detectors. |
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English |
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RPLAB @ alex_kazakov @ |
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1003 |
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Vodolazov, D. Y.; Korneeva, Y. P.; Semenov, A. V.; Korneev, A. A.; Goltsman, G. N. |
Title |
Vortex-assisted mechanism of photon counting in a superconducting nanowire single-photon detector revealed by external magnetic field |
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Journal Article |
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2015 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume ![sorted by Volume (numeric) field, ascending order (up)](img/sort_asc.gif) |
92 |
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10 |
Pages |
104503 (1 to 9) |
Keywords |
SSPD, SNSPD |
Abstract |
We use an external magnetic field to probe the detection mechanism of a superconducting nanowire single-photon detector. We argue that the hot belt model (which assumes partial suppression of the superconducting order parameter Δ across the whole width of the superconducting nanowire after absorption of the photon) does not explain observed weak-field dependence of the photon count rate (PCR) for photons with λ=450nm and noticeable decrease of PCR (with increasing the magnetic field) in a range of the currents for photons with wavelengths λ=450–1200nm. Found experimental results for all studied wavelengths can be explained by the vortex hot spot model (which assumes partial suppression of Δ in the area with size smaller than the width of the nanowire) if one takes into account nucleation and entrance of the vortices to the photon induced hot spot and their pinning by the hot spot with relatively large size and strongly suppressed Δ. |
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1098-0121 |
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1343 |
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Kardakova, A.; Shishkin, A.; Semenov, A.; Goltsman, G. N.; Ryabchun, S.; Klapwijk, T. M.; Bousquet, J.; Eon, D.; Sacépé, B.; Klein, T.; Bustarret, E. |
Title |
Relaxation of the resistive superconducting state in boron-doped diamond films |
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Journal Article |
Year |
2016 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume ![sorted by Volume (numeric) field, ascending order (up)](img/sort_asc.gif) |
93 |
Issue |
6 |
Pages |
064506 |
Keywords |
boron-doped diamond films, resistive superconducting state, relaxation time |
Abstract |
We report a study of the relaxation time of the restoration of the resistive superconducting state in single crystalline boron-doped diamond using amplitude-modulated absorption of (sub-)THz radiation (AMAR). The films grown on an insulating diamond substrate have a low carrier density of about 2.5×1021cm−3 and a critical temperature of about 2K. By changing the modulation frequency we find a high-frequency rolloff which we associate with the characteristic time of energy relaxation between the electron and the phonon systems or the relaxation time for nonequilibrium superconductivity. Our main result is that the electron-phonon scattering time varies clearly as T−2, over the accessible temperature range of 1.7 to 2.2 K. In addition, we find, upon approaching the critical temperature Tc, evidence for an increasing relaxation time on both sides of Tc. |
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1167 |
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Sidorova, M. V.; Kozorezov, A. G.; Semenov, A. V.; Korneeva, Y. P.; Mikhailov, M. Y.; Devizenko, A. Y.; Korneev, A. A.; Chulkova, G. M.; Goltsman, G. N. |
Title |
Nonbolometric bottleneck in electron-phonon relaxation in ultrathin WSi films |
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Journal Article |
Year |
2018 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume ![sorted by Volume (numeric) field, ascending order (up)](img/sort_asc.gif) |
97 |
Issue |
18 |
Pages |
184512 (1 to 13) |
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 τe−ph∼140–190 ps at TC=3.4K, supporting the results of earlier measurements by independent techniques. |
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1305 |
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Sidorova, M.; Semenov, A.; Hübers, H.-W.; Kuzmin, A.; Doerner, S.; Ilin, K.; Siegel, M.; Charaev, I.; Vodolazov, D. |
Title |
Timing jitter in photon detection by straight superconducting nanowires: Effect of magnetic field and photon flux |
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Journal Article |
Year |
2018 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume ![sorted by Volume (numeric) field, ascending order (up)](img/sort_asc.gif) |
98 |
Issue |
13 |
Pages |
134504 (1 to 14) |
Keywords |
SNSPD, NbN namowires |
Abstract |
We studied the effects of the external magnetic field and photon flux on timing jitter in photon detection by straight superconducting NbN nanowires. At two wavelengths 800 and 1560 nm, statistical distribution in the appearance times of photon counts exhibits Gaussian shape at small times and an exponential tail at large times. The characteristic exponential time is larger for photons with smaller energy and increases with external magnetic field while variations in the Gaussian part of the distribution are less pronounced. Increasing photon flux drives the nanowire from the discrete quantum detection regime to the uniform bolometric regime that averages out fluctuations of the total number of nonequilibrium electrons created by the photon and drastically reduces jitter. The difference between standard deviations of Gaussian parts of distributions for these two regimes provides the measure for the strength of electron-number fluctuations; it increases with the photon energy. We show that the two-dimensional hot-spot detection model explains qualitatively the effect of magnetic field. |
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Zhang, X.; Lita, A. E.; Smirnov, K.; Liu, H. L.; Zhu, D.; Verma, V. B.; Nam, S. W.; Schilling, A. |
Title |
Strong suppression of the resistivity near the superconducting transition in narrow microbridges in external magnetic fields |
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Journal Article |
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2020 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume ![sorted by Volume (numeric) field, ascending order (up)](img/sort_asc.gif) |
101 |
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6 |
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060508 (1 to 6) |
Keywords |
MoSi, WSi films |
Abstract |
We have investigated a series of superconducting bridges based on homogeneous amorphous WSi and MoSi films, with bridge widths w ranging from 2 to 1000μm and film thicknesses d∼4−6 and 100 nm. Upon decreasing the bridge widths below the respective Pearl lengths, we observe in all cases distinct changes in the characteristics of the resistive transitions to superconductivity. For each of the films, the resistivity curves R(B,T) separate at a well-defined and field-dependent temperature T∗(B) with decreasing the temperature, resulting in a dramatic suppression of the resistivity and a sharpening of the transitions with decreasing bridge width w. The associated excess conductivity in all the bridges scales as 1/w, which may suggest either the presence of a highly conducting region that is dominating the electric transport, or a change in the vortex dynamics in narrow enough bridges. We argue that this effect can only be observed in materials with sufficiently weak vortex pinning. |
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1800 |
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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 |
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Journal Article |
Year |
2020 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume ![sorted by Volume (numeric) field, ascending order (up)](img/sort_asc.gif) |
102 |
Issue |
5 |
Pages |
054501 (1 to 15) |
Keywords |
NbN SSPD, SNSPD, HEB, bandwidth, relaxation time |
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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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