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Author |
Beck, M.; Klammer, M.; Lang, S.; Leiderer, P.; Kabanov, V. V.; Gol'tsman, G. N.; Demsar, J. |
Title |
Energy-gap dynamics of superconducting NbN thin films studied by time-resolved terahertz spectroscopy |
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Journal Article |
Year |
2011 |
Publication |
Phys. Rev. Lett. |
Abbreviated Journal |
Phys. Rev. Lett. |
Volume |
107 |
Issue |
17 |
Pages |
4 |
Keywords |
NbN thin film, energy gap dynamics |
Abstract |
Using time-domain terahertz spectroscopy we performed direct studies of the photoinduced suppression and recovery of the superconducting gap in a conventional BCS superconductor NbN. Both processes are found to be strongly temperature and excitation density dependent. The analysis of the data with the established phenomenological Rothwarf-Taylor model enabled us to determine the bare quasiparticle recombination rate, the Cooper pair-breaking rate and the electron-phonon coupling constant, λ=1.1±0.1, which is in excellent agreement with theoretical estimates. |
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RPLAB @ gujma @ |
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641 |
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Beck, M.; Rousseau, I.; Klammer, M.; Leiderer, P.; Mittendorff, M.; Winnerl, S.; Helm, M.; Gol'tsman, G.N.; Demsar, J. |
Title |
Transient increase of the energy gap of superconducting NbN thin films excited by resonant narrow-band terahertz pulses |
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Journal Article |
Year |
2013 |
Publication |
Phys. Rev. Lett. |
Abbreviated Journal |
Phys. Rev. Lett. |
Volume |
110 |
Issue |
26 |
Pages |
267003 (1 to 5) |
Keywords |
NbN thin films, energy gap |
Abstract |
Observations of radiation-enhanced superconductivity have thus far been limited to a few type-I superconductors (Al, Sn) excited at frequencies between the inelastic scattering rate and the superconducting gap frequency 2Delta/h. Utilizing intense, narrow-band, picosecond, terahertz pulses, tuned to just below and above 2Delta/h of a BCS superconductor NbN, we demonstrate that the superconducting gap can be transiently increased also in a type-II dirty-limit superconductor. The effect is particularly pronounced at higher temperatures and is attributed to radiation induced nonthermal electron distribution persisting on a 100 ps time scale. |
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Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457, Germany |
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0031-9007 |
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PMID:23848912 |
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1370 |
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Gol'tsman, G. N.; Korneev, A.; Rubtsova, I.; Milostnaya, I.; Chulkova, G.; Minaeva, O.; Smirnov, K.; Voronov, B.; Słysz, W.; Pearlman, A.; Verevkin, A.; Sobolewski, R. |
Title |
Ultrafast superconducting single-photon detectors for near-infrared-wavelength quantum communications |
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Journal Article |
Year |
2005 |
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Phys. Stat. Sol. (C) |
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Phys. Stat. Sol. (C) |
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2 |
Issue |
5 |
Pages |
1480-1488 |
Keywords |
NbN SSPD, SNSPD |
Abstract |
We present our progress on the research and development of NbN superconducting single‐photon detectors (SSPD's) for ultrafast counting of near‐infrared photons for secure quantum communications. Our SSPD's operate in the quantum detection mode based on the photon‐induced hotspot formation and subsequent development of a transient resistive barrier across an ultrathin and submicron‐width superconducting stripe. The devices are fabricated from 4‐nm‐thick NbN films and kept in the 4.2‐ to 2‐K temperature range. The detector experimental quantum efficiency in the photon‐counting mode reaches above 40% for the visible light and up to 30% in the 1.3‐ to 1.55‐µm wavelength range with dark counts below 0.01 per second. The experimental real‐time counting rate is above 2 GHz and is limited by our readout electronics. The SSPD's timing jitter is below 18 ps, and the best‐measured value of the noise‐equivalent power (NEP) is 5 × 10–21 W/Hz1/2 at 1.3 µm. In terms of quantum efficiency, timing jitter, and maximum counting rate, our NbN SSPD's significantly outperform semiconductor avalanche photodiodes and photomultipliers in the 1.3‐ to 1.55‐µm range. |
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1610-1634 |
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1479 |
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Peltonen, J. T.; Peng, Z. H.; Korneeva, Yu. P.; Voronov, B. M.; Korneev, A. A.; Semenov, A. V.; Gol'tsman, G. N.; Tsai, J. S; Astafiev, Oleg |
Title |
Coherent dynamics and decoherence in a superconducting weak link |
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Journal Article |
Year |
2016 |
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Physic. Rev. B, |
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Physic. Rev. B, |
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94 |
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180508 |
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RPLAB @ akorneev @ |
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1123 |
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Aksaev, E. E.; Gershenzon, E.M.; Gol'tsman, G. N.; Mirskij, G. I.; Semenov, A. D. |
Title |
Submillimetric spectrometer-relaxometer based on backward-wave tubes with picosecond time resolution |
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Journal Article |
Year |
1991 |
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Pribory i Tekhnika Eksperimenta |
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Pribory i Tekhnika Eksperimenta |
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34 |
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2 |
Pages |
125-131 |
Keywords |
BWO, applications |
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The high-sensitive automatic spectrometer-relaxometer based on backward-wave tubes in the range of 4÷0.25 mm was described permitting to study the response kinetics of sample under investigation in any point of this range with the resolution time of 10-11 s. The relaxation measurements were conducted using oscillation beats of two adequate tubes, the frequency of one of them was fixed, while that of the other one was changeable. The amplitude-frequency characteristic of the response under the conditions of synchronous reception was recorded at beat frequency variation from 107 to 1010 Hz. The high sensitivity was reached by decreasing the device recording band down to 100 Hz in the whole measuring range. |
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0032-8162 |
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1683 |
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Gershenzon, E. M.; Gol'tsman, G. N.; Mirskii, G. I. |
Title |
Submillimeter backward-wave-tube spectrometer-relaxometer |
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Journal Article |
Year |
1987 |
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Pribory i Tekhnika Eksperimenta |
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Pribory i Tekhnika Eksperimenta |
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30 |
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4 |
Pages |
131-137 |
Keywords |
BWO, applications |
Abstract |
A backward-wave-tube (BWT) spectrometer-relaxometer is described that is designed for study of the relaxation characteristics of photoconductors in the wavelength range of 2-0.25 mm – in particular, to measure the relaxation times of the submillimeter photoconductivity of germanium in the range of 10[sup:-4]-10[sup:-9] sec and to determine from these data the concentration of compensating impurities of from 10[sup:10] to 10[sup:14] cm[sup:-3]. The instrument uses the beats of the oscillations of two BWTs and records the amplitude-frequency response of the specimen with variation of the beat frequency from 10[sup:4] to 10[sup:8] Hz with accumulation of the desired signal for less than or equal to1 sec by means of a quadrature synchronous detector. The beat frequency is stabilized and the quadrature voltages of the synchronous detector are formed by means of phase-locked loops. |
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1699 |
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Gershenzon, E. M.; Gol'tsman, G. N.; Semenov, A. D. |
Title |
Submillimeter backward wave tube spectrometer for measuring superconducting film transmission |
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Journal Article |
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1983 |
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Pribory i Tekhnika Eksperimenta |
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Pribory i Tekhnika Eksperimenta |
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26 |
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5 |
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134-137 |
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BWO spectroscopy, spectrometer, transmission |
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A spectrometer employing six backward wave tubes is described. It is intended for investigation of superconductors in the 0.2-3 mm range of wave lengths. During the measurement of the transmission spectrum it is possible to determine the energy gap for superconduct1ng films 50 to 4000 A thick. The transmission factor can vary from 10-1 to 10-9. Spectrum of relation of film transmission factors in superconducting and normal states is measured for determining the energy gap 2 Δ. The transmission spectrum obtained by means of a computer for vanadium film 300 A thick is given as an example. The energy gap 2 Δ = 1.4 MeV |
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0032-8162 |
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Субмиллиметровый спектрометр с лампами обратной волны для измерения пропускания сверхпроводниковых пленок |
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1713 |
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Cherednichenko, S.; Ronnung, F.; Gol'tsman, G.; Gershenzon, E.; Winkler, D. |
Title |
YBa2Cu3O7-δ hot-electron bolometer with submicron dimensions |
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Conference Article |
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1999 |
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Proc. 10th Int. Symp. Space Terahertz Technol. |
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Proc. 10th Int. Symp. Space Terahertz Technol. |
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181-189 |
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YBCO HTS HEB mixers |
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Photoresponse of YBa2Cu3O7-δ hot-electron bolometers to modulated near-infrared radiation was studied at a modulation .frequenc y var y ing from 0.2 MHz to 2 GHz. Bolometers were _fabricated from a 50 12 M thick film and had in-plane areas of 10x10 , um 2 . 2x0.2 s um', 1x0.2 p.m', and 0.5x0.2 jim. We found that nonequilibrium phonons cool down more effectively for the bolometers with smaller area. For the smallest bolometer the bolometric component in the response is 10 dB less than for the largest one. |
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1572 |
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Schubert, J.; Semenov, A.; Gol'tsman, G.; Hübers, H.-W.; Schwaab, G.; Voronov, B.; Gershenzon, E. |
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Noise temperature and sensitivity of a NbN hot-electron mixer at frequencies from 0.7 THz to 5.2 THz |
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Conference Article |
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1999 |
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Proc. 10th Int. Symp. Space Terahertz Technol. |
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Proc. 10th Int. Symp. Space Terahertz Technol. |
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190-199 |
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NbN HEB mixers |
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We report on noise temperature measurements of a NbN phonon-cooled hot-electron bolometric mixer at different bias regimes. The device was a 3 nm thick bridge with in-plane dimensions of 1.7 x 0.2 gm 2 integrated in a complementary logarithmic spiral antenna. Measurements were performed at frequencies ranging from 0.7 THz up to 5.2 THz. The measured DSB noise temperatures are 1500 K (0.7 THz), 2200 K (1.4 THz), 2600 K (1.6 THz), 2900 K (2.5 THz), 4000 K (3.1 THz) 5600 K (4.3 THz) and 8800 K (5.2 THz). Two bias regimes are possible in order to achieve low noise temperatures. But only one of them yields sensitivity fluctuations close to the theoretical limit. |
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1573 |
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Gerecht, E.; Musante, C. F.; Jian, H.; Zhuang, Y.; Yngvesson, K. S.; Dickinson, J.; Goyette, T.; Waldman, J.; Yagoubov, P. A.; Gol'tsman, G. N.; Voronov, B. M.; Gershenzon, E. M. |
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Improved characteristics of NbN HEB mixers integrated with log-periodic antennas |
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Conference Article |
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1999 |
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Proc. 10th Int. Symp. Space Terahertz Technol. |
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Proc. 10th Int. Symp. Space Terahertz Technol. |
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200-207 |
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NbN HEB mixers |
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1574 |
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