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Author Vercruyssen, N.; Verhagen, T. G. A.; Flokstra, M. G.; Pekola, J. P.; Klapwijk, T. M. openurl 
  Title Evanescent states and nonequilibrium in driven superconducting nanowires Type Journal Article
  Year 2012 Publication 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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  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 898  
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Author Gao, J. R.; Hovenier, J. N.; Yang, Z. Q.; Baselmans, J. J. A.; Baryshev, A.; Hajenius, M.; Klapwijk, T. M.; Adam, A. J. L.; Klaassen, T. O.; Williams, B. S.; Kumar, S.; Hu, Q.; Reno, J. L. openurl 
  Title Terahertz heterodyne receiver based on a quantum cascade laser and a superconducting bolometer Type Journal Article
  Year 2005 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.  
  Volume 86 Issue Pages 244104 (1 to 3)  
  Keywords HEB, QCL  
  Abstract We report the first demonstration of an all solid-stateheterodyne receiver that can be used for high-resolution spectroscopy above 2THz suitable for space-based observatories. The receiver uses a NbN superconducting hot-electron bolometer as mixer and a quantum cascade laser operating at 2.8THz as local oscillator. We measure a double sideband receiver noise temperature of 1400K at 2.8THz and 4.2K, and find that the free-running QCL has sufficient power stability for a practical receiver, demonstrating an unprecedented combination of sensitivity and stability.  
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  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 905  
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Author Klapwijk, T. M.; Barends, R.; Gao, J. R.; Hajenius, M.; Baselmans, J. J. A. openurl 
  Title Improved superconducting hot-electron bolometer devices for the THz range Type Conference Article
  Year 2004 Publication Proc. SPIE Abbreviated Journal Proc. SPIE  
  Volume 5498 Issue Pages 129-139  
  Keywords HEB mixer distributed model, numerical model  
  Abstract Improved and reproducible heterodyne mixing (noise temperatures of 950 K at 2.5 THz) has been realized with NbN based hot-electron superconducting devices with low contact resistances. A distributed temperature numerical model of the NbN bridge, based on a local electron and a phonon temperature, has been used to understand the physical conditions during the mixing process. We find that the mixing is predominantly due to the exponential rise of the local resistivity as a function of electron temperature.  
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  Area Expedition Conference  
  Notes Invited talk, Recommended by Klapwijk Approved no  
  Call Number Serial 912  
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Author Romijn, J.; Klapwijk, T. M.; Renne, M. J.; Mooij, J. E. doi  openurl
  Title Critical pair-breaking current in superconducting aluminum strips far below Tc Type Journal Article
  Year 1982 Publication 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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  Area Expedition Conference  
  Notes Recommended by Klapwijk Approved no  
  Call Number Serial 925  
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Author Lobanov, Y.; Shcherbatenko, M.; Finkel, M.; Maslennikov, S.; Semenov, A.; Voronov, B. M.; Rodin, A. V.; Klapwijk, T. M.; Gol'tsman, G. N. doi  openurl
  Title NbN hot-electron-bolometer mixer for operation in the near-IR frequency range Type Journal Article
  Year 2015 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.  
  Volume 25 Issue 3 Pages 2300704 (1 to 4)  
  Keywords HEB mixer, IR, optical antenna  
  Abstract Traditionally, hot-electron-bolometer (HEB) mixers are employed for THz and “super-THz” heterodyne detection. To explore the near-IR spectral range, we propose a fiber-coupled NbN film based HEB mixer. To enhance the incident-light absorption, a quasi-antenna consisting of a set of parallel stripes of gold is used. To study the antenna effect on the mixer performance, we have experimentally studied a set of devices with different size of the Au stripe and spacing between the neighboring stripes. With use of the well-known isotherm technique we have estimated the absorption efficiency of the mixer, and the maximum efficiency has been observed for devices with the smallest pitch of the alternating NbN and NbN-Au stripes. Also, a proper alignment of the incident Eâƒ<2014>-field with respect to the stripes allows us to improve the coupling further. Studying IV-characteristics of the mixer under differently-aligned Eâƒ<2014>-field of the incident radiation, we have noticed a difference in their shape. This observation suggests that a difference exists in the way the two waves with orthogonal polarizations parallel and perpendicular Eâƒ<2014>-field to the stripes heat the electrons in the HEB mixer. The latter results in a variation in the electron temperature distribution over the HEB device irradiated by the two waves.  
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  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 952  
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Author Seliverstov, S.; Maslennikov, S.; Ryabchun, S.; Finkel, M.; Klapwijk, T. M.; Kaurova, N.; Vachtomin, Yu.; Smirnov, K.; Voronov, B.; Goltsman, G. doi  openurl
  Title Fast and sensitive terahertz direct detector based on superconducting antenna-coupled hot electron bolometer Type Journal Article
  Year 2015 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.  
  Volume 25 Issue 3 Pages 2300304  
  Keywords HEB detector responsivity, HEB model, numerical calculations, numerical model  
  Abstract We characterize superconducting antenna-coupled hot-electron bolometers for direct detection of terahertz radiation operating at a temperature of 9.0 K. The estimated value of responsivity obtained from lumped-element theory is strongly different from the measured one. A numerical calculation of the detector responsivity is developed, using the Euler method, applied to the system of heat balance equations written in recurrent form. This distributed element model takes into account the effect of nonuniform heating of the detector along its length and provides results that are in better agreement with the experiment. At a signal frequency of 2.5 THz, the measured value of the optical detector noise equivalent power is 2.0 × 10-13 W · Hz-0.5. The value of the bolometer time constant is 35 ps. The corresponding energy resolution is about 3 aJ. This detector has a sensitivity similar to that of the state-of-the-art sub-millimeter detectors operating at accessible cryogenic temperatures, but with a response time several orders of magnitude shorter.  
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  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 953  
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Author Hajenius, M.; Barends, R.; Gao, J. R.; Klapwijk, T. M.; Baselmans, J. J. A.; Baryshev, A.; Voronov, B.; Gol'tsman, G. doi  openurl
  Title Local resistivity and the current-voltage characteristics of hot electron bolometer mixers Type Journal Article
  Year 2005 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.  
  Volume 15 Issue 2 Pages 495-498  
  Keywords HEB mixer distributed model, HEB distributed model, distributed HEB model  
  Abstract Hot-electron bolometer devices, used successfully in low noise heterodyne mixing at frequencies up to 2.5 THz, have been analyzed. A distributed temperature numerical model of the NbN bridge, based on a local electron and a phonon temperature, is used to model pumped IV curves and understand the physical conditions during the mixing process. We argue that the mixing is predominantly due to the strongly temperature dependent local resistivity of the NbN. Experimentally we identify the origins of different transition temperatures in a real HEB device, suggesting the importance of the intrinsic resistive transition of the superconducting bridge in the modeling.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1051-8223 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 980  
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Author Heslinga, D. R.; Shafranjuk, S. E.; van Kempen, H.; Klapwijk, T. M. url  doi
openurl 
  Title Observation of double-gap-edge Andreev reflection at Si/Nb interfaces by point-contact spectroscopy Type Journal Article
  Year 1994 Publication 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.  
  Address (up)  
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  Publisher American Physical Society Place of Publication Editor  
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  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1005  
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Author Bueno, J.; Coumou, P. C. J. J.; Zheng, G.; de Visser, P. J.; Klapwijk, T. M.; Driessen, E. F. C.; Doyle, S.; Baselmans, J. J. A openurl 
  Title Anomalous response of superconducting titanium nitride resonators to terahertz radiation Type Journal Article
  Year 2014 Publication Appl. Phys. Lett. Abbreviated Journal  
  Volume 105 Issue Pages 192601 (1 to 5)  
  Keywords KID, TiN, NEP, disordered superconductors, inhomogeneous state  
  Abstract We present an experimental study of kinetic inductance detectors (KIDs) fabricated of atomic layer deposited TiN films and characterized at radiation frequencies of 350 GHz. The responsivity to radiation is measured and found to increase with the increase in radiation powers, opposite to what is expected from theory and observed for hybrid niobium titanium nitride/aluminium (NbTiN/Al) and all-aluminium (all-Al) KIDs. The noise is found to be independent of the level of the radiation power. The noise equivalent power improves with higher radiation powers, also opposite to what is observed and well understood for hybrid NbTiN/Al and all-Al KIDs. We suggest that an inhomogeneous state of these disordered superconductors should be used to explain these observations.  
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  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1068  
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Author Coumou, P. C. J. J.; Driessen, E. F. C.; Bueno, J.; Chapelier, C.; Klapwijk, T. M. url  doi
openurl 
  Title Electrodynamic response and local tunneling spectroscopy of strongly disordered superconducting TiN films Type Journal Article
  Year 2013 Publication 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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  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1069  
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