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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. |
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Title |
Electron energy relaxation in disordered superconducting NbN films |
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Year |
2020 |
Publication |
Phys. Rev. B |
Abbreviated Journal  |
Phys. Rev. B |
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Volume |
102 |
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5 |
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054501 (1 to 15) |
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Keywords |
NbN SSPD, SNSPD, HEB, bandwidth, relaxation time |
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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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2469-9950 |
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1266 |
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Lusche, R.; Semenov, A.; Korneeva, Y.; Trifonov, A.; Korneev, A.; Gol'tsman, G.; Hübers, H.-W. |
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Title |
Effect of magnetic field on the photon detection in thin superconducting meander structures |
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Journal Article |
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Year |
2014 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
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Volume |
89 |
Issue |
10 |
Pages |
104513 (1 to 7) |
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Keywords |
NbN SSPD, SNSPD |
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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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1098-0121 |
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1367 |
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Zhang, J.; Słysz, W.; Pearlman, A.; Verevkin, A.; Sobolewski, R.; Okunev, O.; Chulkova, G.; Gol’tsman, G. N. |
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Time delay of resistive-state formation in superconducting stripes excited by single optical photons |
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2003 |
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Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
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67 |
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13 |
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132508 (1 to 4) |
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NbN SSPD, SNSPD |
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We have observed a 65(±5)-ps time delay in the onset of a resistive-state formation in 10-nm-thick, 130-nm-wide NbN superconducting stripes exposed to single photons. The delay in the photoresponse decreased to zero when the stripe was irradiated by multi-photon (classical) optical pulses. Our NbN structures were kept at 4.2 K, well below the material’s critical temperature, and were illuminated by 100-fs-wide optical pulses. The time-delay phenomenon has been explained within the framework of a model based on photon-induced generation of a hotspot in the superconducting stripe and subsequent, supercurrent-assisted, resistive-state formation across the entire stripe cross section. The measured time delays in both the single-photon and two-photon detection regimes agree well with theoretical predictions of the resistive-state dynamics in one-dimensional superconducting stripes. |
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0163-1829 |
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1519 |
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Baeva, E. M.; Sidorova, M. V.; Korneev, A. A.; Smirnov, K. V.; Divochy, A. V.; Morozov, P. V.; Zolotov, P. I.; Vakhtomin, Y. B.; Semenov, A. V.; Klapwijk, T. M.; Khrapai, V. S.; Goltsman, G. N. |
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Title |
Thermal properties of NbN single-photon detectors |
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2018 |
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Phys. Rev. Applied |
Abbreviated Journal |
Phys. Rev. Applied |
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10 |
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6 |
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064063 (1 to 8) |
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Keywords |
NbN SSPD, SNSPD |
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We investigate thermal properties of a NbN single-photon detector capable of unit internal detection efficiency. Using an independent calibration of the coupling losses, we determine the absolute optical power absorbed by the NbN film and, via resistive superconductor thermometry, the temperature dependence of the thermal resistance Z(T) of the NbN film. In principle, this approach permits simultaneous measurement of the electron-phonon and phonon-escape contributions to the energy relaxation, which in our case is ambiguous because of the similar temperature dependencies. We analyze Z(T) with a two-temperature model and impose an upper bound on the ratio of electron and phonon heat capacities in NbN, which is surprisingly close to a recent theoretical lower bound for the same quantity in similar devices. |
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2331-7019 |
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1226 |
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Korneeva, Y. P.; Vodolazov, D. Y.; Semenov, A. V.; Florya, I. N.; Simonov, N.; Baeva, E.; Korneev, A. A.; Goltsman, G. N.; Klapwijk, T. M. |
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Title |
Optical single-photon detection in micrometer-scale NbN bridges |
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Journal Article |
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2018 |
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Phys. Rev. Applied |
Abbreviated Journal |
Phys. Rev. Applied |
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Volume |
9 |
Issue |
6 |
Pages |
064037 (1 to 13) |
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Keywords |
NbN SSPD, SNSPD |
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We demonstrate experimentally that single-photon detection can be achieved in micrometer-wide NbN bridges, with widths ranging from 0.53 to 5.15 μm and for photon wavelengths of 408 to 1550 nm. The microbridges are biased with a dc current close to the experimental critical current, which is estimated to be about 50% of the theoretically expected depairing current. These results offer an alternative to the standard superconducting single-photon detectors, based on nanometer-scale nanowires implemented in a long meandering structure. The results are consistent with improved theoretical modeling based on the theory of nonequilibrium superconductivity, including the vortex-assisted mechanism of initial dissipation. |
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2331-7019 |
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1303 |
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