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Kitaygorsky, J.; Zhang, J.; Verevkin, A.; Sergeev, A.; Korneev, A.; Matvienko, V.; Kouminov, P.; Smirnov, K.; Voronov, B.; Gol'tsman, G.; Sobolewski, R. |
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Title |
Origin of dark counts in nanostructured NbN single-photon detectors |
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Journal Article |
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2005 |
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IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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Volume |
15 |
Issue |
2 |
Pages |
545-548 |
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SSPD dark counts, SNSPD, dark counts rate |
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We present our study of dark counts in ultrathin (3.5 to 10 nm thick), narrow (120 to 170 nm wide) NbN superconducting stripes of different lengths. In experiments, where the stripe was completely isolated from the outside world and kept at temperature below the critical temperature Tc, we detected subnanosecond electrical pulses associated with the spontaneous appearance of the temporal resistive state. The resistive state manifested itself as generation of phase-slip centers (PSCs) in our two-dimensional superconducting stripes. Our analysis shows that not far from Tc, PSCs have a thermally activated nature. At lowest temperatures, far below Tc, they are created by quantum fluctuations. |
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1057 |
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Skalare, A.; McGrath, William R.; Echternach, P. M.; Leduc, H. G.; Siddiqi, I.; Verevkin, A.; Prober, D. E. |
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Title |
Aluminum hot-electron bolometer mixers at submillimeter wavelengths |
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Journal Article |
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2001 |
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IEEE Trans. Appl. Supercond. |
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11 |
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1 |
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641-644 |
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Al HEB mixer, contacts, interface, in situ, in-situ, Aluminium HEB mixer |
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Diffusion-cooled aluminum hot-electron bolometer (HEB) mixers are of interest for low-noise high resolution THz-frequency spectroscopy within astrophysics. Al HEB mixers offer operation with an order of magnitude less local oscillator power, higher intermediate frequency bandwidth and potentially lower noise than competing devices made from other materials. We report on mixer experiments at 618 GHz with devices fabricated from films with sheet resistances in the range from about 55 Ω down to about 9 Ω per square. Intermediate frequency bandwidths of up to 3 GHz were measured (1 μm long device), with absorbed local oscillator power levels of 0.5 to 6 nW and mixer conversion up to -21.5 dB. High input coupling efficiency implies that the electrons in the device are able to thermalize before escaping from the device. It was found that the long coherence length complicates mixer operations due to the proximity of the contact pads. Also, saturation at the IF frequency may be a concern for this type of device, and warrants further studies. |
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1051-8223 |
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ref919426b |
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1061 |
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Shangina, E. L.; Smirnov, K. V.; Morozov, D. V.; Kovalyuk, V. V.; Gol’tsman, G. N.; Verevkin, A. A.; Toropov, A. I. |
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Frequency bandwidth and conversion loss of a semiconductor heterodyne receiver with phonon cooling of two-dimensional electrons |
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2010 |
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Semicond. |
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Semicond. |
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44 |
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11 |
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1427-1429 |
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2DEG, AlGaAs/GaAs heterostructures mixers |
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The temperature and concentration dependences of the frequency bandwidth of terahertz heterodyne AlGaAs/GaAs detectors based on hot electron phenomena with phonon cooling of two-dimensional electrons have been measured by submillimeter spectroscopy with a high time resolution. At a temperature of 4.2 K, the frequency bandwidth at a level of 3 dB (f 3 dB) is varied from 150 to 250 MHz with a change in the concentration n s according to the power law f 3dB ∝ n −0.5 s due to the dominant contribution of piezoelectric phonon scattering. The minimum conversion loss of the semiconductor heterodyne detector is obtained in structures with a high carrier mobility (μ > 3 × 105 cm2 V−1 s−1 at 4.2 K). |
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1063-7826 |
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Полоса и потери преобразования полупроводникового смесителя с фононным каналом охлаждения двумерных электронов |
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1216 |
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Shangina, E. L.; Smirnov, K. V.; Morozov, D. V.; Kovalyuk, V. V.; Gol’tsman, G. N.; Verevkin, A. A.; Toropov, A. I. |
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Concentration dependence of the intermediate frequency bandwidth of submillimeter heterodyne AlGaAs/GaAs nanostructures |
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Journal Article |
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2010 |
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Bull. Russ. Acad. Sci. Phys. |
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Bull. Russ. Acad. Sci. Phys. |
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74 |
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1 |
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100-102 |
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2DEG AlGaAs/GaAs heterostructures, THz heterodyne detectors, IF bandwidth |
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The concentration dependence of the intermediate frequency bandwidth of heterodyne AlGaAs/GaAs detectors with 2D electron gas is measured using submillimeter spectroscopy with high time resolution at T= 4.2 K. The intermediate frequency bandwidth f3dBfalls from 245 to 145 MHz with increasing concentration of 2D electrons n s = (1.6-6.6) × 10[su11] cm-2. The dependence f3dB ≈ n s – 0.04±is observed in the studied concentration range; this dependence is determined by electron scattering by the deformation potential of acoustic phonons and piezoelectric scattering. |
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1062-8738 |
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1217 |
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Bell, M.; Sergeev, A.; Mitin, V.; Bird, J.; Verevkin, A.; Gol’tsman, G. |
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Title |
One-dimensional resistive states in quasi-two-dimensional superconductors: Experiment and theory |
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Journal Article |
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2007 |
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Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
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76 |
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9 |
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094521 (1 to 5) |
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Keywords |
uasi-two-dimensional superconductors, NbN |
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We investigate competition between one- and two-dimensional topological excitations—phase slips and vortices—in the formation of resistive states in quasi-two-dimensional superconductors in a wide temperature range below the mean-field transition temperature TC0. The widths w=100nm of our ultrathin NbN samples are substantially larger than the Ginzburg-Landau coherence length ξ=4nm, and the fluctuation resistivity above TC0 has a two-dimensional character. However, our data show that the resistivity below TC0 is produced by one-dimensional excitations—thermally activated phase slip strips (PSSs) overlapping the sample cross section. We also determine the scaling phase diagram, which shows that even in wider samples the PSS contribution dominates over vortices in a substantial region of current and/or temperature variations. Measuring the resistivity within 7 orders of magnitude, we find that the quantum phase slips can only be essential below this level. |
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1098-0121 |
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1423 |
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