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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 Type Journal Article
Year 2012 Publication (up) Phys. Rev. B Abbreviated Journal Phys. Rev. B
Volume 85 Issue Pages 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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Call Number Serial 898
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Author Romijn, J.; Klapwijk, T. M.; Renne, M. J.; Mooij, J. E.
Title Critical pair-breaking current in superconducting aluminum strips far below Tc Type Journal Article
Year 1982 Publication (up) Phys. Rev. B Abbreviated Journal Phys. Rev. B
Volume 26 Issue 7 Pages 3648-3655
Keywords superconducting nanowire
Abstract Critical currents of narrow, thin aluminum strips have been measured as a function of temperature. For the smallest samples uniformity of the current density is obtained over a large temperature range. Hence the intrinsic limit on the currentcarrying capacity of the superconductor was measured outside the Ginzburg-Landau -regime. The experimental values are compared with recent theoretical predictions by Kupriyanov and Lukichev. An approximate method of solving their equations is given, the results of which agree with the exact solution to within 1%. Experimental data are in excellent agreement with theoretical predictions. The absolute values agree if one assumes a ρl value of 4×10–16 Ωm2 with vF=1.3×106 m/s. This value for ρl is the same as that found from measurements of the anomalous skin effect but differs from values extracted from size-effect-limited resistivity.
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Notes Recommended by Klapwijk Approved no
Call Number Serial 925
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Author Heslinga, D. R.; Shafranjuk, S. E.; van Kempen, H.; Klapwijk, T. M.
Title Observation of double-gap-edge Andreev reflection at Si/Nb interfaces by point-contact spectroscopy Type Journal Article
Year 1994 Publication (up) Phys. Rev. B Abbreviated Journal Phys. Rev. B
Volume 49 Issue 15 Pages 10484-10494
Keywords Nb, Si, Nb-Si, Nb/Si, Si/Nb, Andreev reflection, point-contact spectroscopy
Abstract Andreev reflection point-contact spectroscopy is performed on a bilayer consisting of 50-nm degenerately doped Si backed with Nb. Due to the short mean free path both injection into and transport across the Si layer are diffusive, in contrast to the ballistic conditions prevailing in clean metal layers. Nevertheless a large Andreev signal is observed in the point-contact characteristics, not reduced by elastic scattering in the Si layer or by interface scattering, but only limited by the transmission coefficient of the metal-semiconductor point contact. Two peaks in the Andreev reflection probability are visible, marking the values of the superconducting energy gap at the interface on the Nb and Si sides. This interpretation is supported by a method of solving the Bogolubov equations analytically using a simplified expression for the variation of the order parameter close to the interface. This observation enables a comparison with theoretical predictions of the gap discontinuity in the proximity effect. It is found that the widely used de Gennes model does not agree with the experimental data.
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Publisher American Physical Society Place of Publication Editor
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Notes Approved no
Call Number Serial 1005
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Author Coumou, P. C. J. J.; Driessen, E. F. C.; Bueno, J.; Chapelier, C.; Klapwijk, T. M.
Title Electrodynamic response and local tunneling spectroscopy of strongly disordered superconducting TiN films Type Journal Article
Year 2013 Publication (up) Phys. Rev. B Abbreviated Journal
Volume 88 Issue 18 Pages 180505 (1 to 5)
Keywords strongly disordered superconducting TiN films, microwave resonators
Abstract We have studied the electrodynamic response of strongly disordered superconducting TiN films using microwave resonators, where the disordered superconductor is the resonating element in a high-quality superconducting environment of NbTiN. We describe the response assuming an effective pair-breaking mechanism modifying the density of states and compare this to local tunneling spectra obtained using scanning tunneling spectroscopy. For the least disordered film (kFl=8.7, Rs=13Ω), we find good agreement, whereas for the most disordered film (kFl=0.82, Rs=4.3kΩ), there is a strong discrepancy, which signals the breakdown of a model based on uniform properties.
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Notes Approved no
Call Number Serial 1069
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Author 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 Type Journal Article
Year 2016 Publication (up) Phys. Rev. B Abbreviated Journal Phys. Rev. B
Volume 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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ISSN 2469-9950 ISBN Medium
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Notes Approved no
Call Number Serial 1167
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