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Beck, M.; Klammer, M.; Rousseau, I.; Gol’tsman, G. N.; Diamant, I.; Dagan, Y.; Demsar, J. |
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Title |
Probing superconducting gap dynamics with THz pulses |
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Conference Article |
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Year |
2015 |
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CLEO |
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CLEO |
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SM3H.3 (1 to 2) |
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Keywords |
superconducting gap; electric fields; femtosecond pulses; near infrared radiation; picosecond pulses; superconductors; thin films |
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We studied superconducting gap dynamics in a BCS superconductor NbN and electron doped cuprate superconductor PCCO following excitation with near-infrared (NIR) and narrow band THz pulses. Systematic studies on PCCO imply very selective electron-phonon coupling. |
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Optical Society of America |
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1345 |
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Author |
Beck, M.; Rousseau, I.; Klammer, M.; Leiderer, P.; Mittendorff, M.; Winnerl, S.; Helm, M.; Gol'tsman, G.N.; Demsar, J. |
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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 |
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Year |
2013 |
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Phys. Rev. Lett. |
Abbreviated Journal |
Phys. Rev. Lett. |
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110 |
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26 |
Pages |
267003 (1 to 5) |
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Keywords |
NbN thin films, energy gap |
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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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Beck, Matthias; Leiderer, Paul; Kabanov, Viktor V.; Gol'tsman, Gregory; Helm, Manfred; Demsar, Jure |
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Energy-gap dynamics of a superconductor NbN studied by time-resolved terahertz spectroscopy |
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2012 |
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INIS |
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45 |
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12 |
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1-3 |
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Keywords |
NbN energy gap |
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Using time-resolved terahertz (THz) spectroscopy we performed direct studies of the photoinduced suppression and recovery of the SC gap in a conventional SC 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 important microscopic constants: the Cooper pair-breaking rate via phonon absorption and the bare quasiparticle recombination rate. From the latter we were able to extract the dimensionless electron-phonon coupling constant, λ=1.1±0.1, in excellent agreement with theoretical estimates. The technique also allowed us to determine the absorbed energy required to suppress SC, which in NbN equals the thermodynamic condensation energy (in cuprates the two differ by an order of magnitude). Finally, we present the first studies of dynamics following resonant excitation with intense narrow band THz pulses tuned to above and below the superconducting gap. These suggest an additional process, particularly pronounced near Tc, that could be attributed to amplification of SC via effective quasiparticle cooling. |
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1383 |
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Beebe, M. R.; Beringer, D. B.; Burton, M. C.; Yang, K.; Lukaszew, R. A. |
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Title |
Stoichiometry and thickness dependence of superconducting properties of niobium nitride thin films |
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Journal Article |
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Year |
2016 |
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Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films |
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Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films |
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34 |
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2 |
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021510 (1 to 4) |
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Keywords |
potential plagiarism, possible plagiarism, NbN films |
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The current technology used in linear particle accelerators is based on superconducting radio frequency (SRF) cavities fabricated from bulk niobium (Nb), which have smaller surface resistance and therefore dissipate less energy than traditional nonsuperconducting copper cavities. Using bulk Nb for the cavities has several advantages, which are discussed elsewhere; however, such SRF cavities have a material-dependent accelerating gradient limit. In order to overcome this fundamental limit, a multilayered coating has been proposed using layers of insulating and superconducting material applied to the interior surface of the cavity. The key to this multilayered model is to use superconducting thin films to exploit the potential field enhancement when these films are thinner than their London penetration depth. Such field enhancement has been demonstrated in MgB2 thin films; here, the authors consider films of another type-II superconductor, niobium nitride (NbN). The authors present their work correlating stoichiometry and superconducting properties in NbN thin films and discuss the thickness dependence of their superconducting properties, which is important for their potential use in the proposed multilayer structure. While there are some previous studies on the relationship between stoichiometry and critical temperature TC, the authors are the first to report on the correlation between stoichiometry and the lower critical field HC1. |
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0734-2101 |
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Potential plagiarism for 1503 |
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1504 |
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Bell, M.; Kaurova, N.; Divochiy, A.; Gol'tsman, G.; Bird, J.; Sergeev, A.; Verevkin, A. |
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Title |
On the nature of resistive transition in disordered superconducting nanowires |
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Journal Article |
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Year |
2007 |
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IEEE Trans. Appl. Supercond. |
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IEEE Trans. Appl. Supercond. |
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17 |
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2 |
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267-270 |
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SSPD, SNSPD |
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Hot-electron single-photon counters based on long superconducting nanowires are starting to become popular in optical and infrared technologies due to their ultimately high sensitivity and very high response speed. We investigate intrinsic fluctuations in long NbN nanowires in the temperature range of 4.2 K-20 K, i.e. above and below the superconducting transition. These fluctuations are responsible for fluctuation resistivity and also determine the noise in practical devices. Measurements of the fluctuation resistivity were performed at low current densities and also in external magnetic fields up to 5 T. Above the BCS critical temperature T co the resistivity is well described by the Aslamazov-Larkin (AL) theory for two-dimensional samples. Below T co the measured resistivity is in excellent agreement with the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory developed for one-dimensional superconductors. Despite that our nanowires of 100 nm width are two-dimensional with respect to the coherence length, our analysis shows that at relatively low current densities the one-dimensional LAMH mechanism based on thermally induced phase slip centers dominates over the two-dimensional mechanism related to unbinding of vortex-antivortex pairs below the Berezinskii-Kosterlitz-Thouless transition. |
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1051-8223 |
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1247 |
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