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Vercruyssen, N.; Verhagen, T. G. A.; Flokstra, M. G.; Pekola, J. P.; Klapwijk, T. M. |
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Evanescent states and nonequilibrium in driven superconducting nanowires |
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2012 |
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Phys. Rev. B |
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Phys. Rev. B |
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85 |
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224503(1-10) |
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Al HEB, Al superconducting nanowire, global state, bimodal state, quasiclassical kinetic equations, Usadel equation |
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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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898 |
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Baselmans, J. J. A.; Hajenius, M.; Gao, J. R.; Klapwijk, T. M.; de Korte, P. A. J.; Voronov, B.; Gol'tsman, G. |
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Title |
Doubling of sensitivity and bandwidth in phonon cooled hot electron bolometer mixers |
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Journal Article |
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2004 |
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Appl. Phys. Lett. |
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Appl. Phys. Lett. |
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84 |
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11 |
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1958-1960 |
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NbN HEB mixers |
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We demonstrate that the performance of NbN lattice cooled hot electron bolometer mixers depends strongly on the interface quality between the bolometer and the contact structure. We show experimentally that both the receiver noise temperature and the gain bandwidth can be improved by more than a factor of 2 by cleaning the interface and adding an additional superconducting interlayer to the contact pad. Using this we obtain a double sideband receiver noise temperature TN,DSB=950 K
at 2.5 THz and 4.3 K, uncorrected for losses in the optics. At the same bias point, we obtain an IF gain bandwidth of 6 GHz. |
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Siddiqi, I.; Prober, D. E. |
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Nb–Au bilayer hot-electron bolometers for low-noise THz heterodyne detection |
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2004 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
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84 |
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8 |
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1404 |
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HEB, mixers, dynamic range, saturation, LO power, local oscillator power, Nb |
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The sensitivity of present Nb diffusion-cooled hot-electron bolometer (HEB) mixers is not quantum limited, and can be improved by reducing the superconducting transition temperature TC. Lowering TC reduces thermal fluctuations, resulting in a decrease of the mixer noise temperature TM. However, lower TC mixers have reduced dynamic range and saturate more easily due to background noise. We present 30 GHz microwave measurements on a bilayer HEB system, Nb–Au, in which TC can be tuned with Au layer thickness to obtain the maximum sensitivity for a given noise background. These measurements are intended as a guide for the optimization of THz mixers. Using a Nb–Au mixer with TC = 1.6 K, we obtain TM = 50 K with 2 nW of local oscillator (LO) power. Good mixer performance is observed over a wide range of LO power and bias voltage and such a device should not exhibit saturation in a THz receiver. |
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0003-6951 |
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Смирнов, А. В.; Карманцов, М. С.; Смирнов, К. В.; Вахтомин, Ю. Б.; Мастеров, Д. В.; Тархов, М. А.; Павлов, С. А.; Парафин, А. Е. |
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Терагерцовый отклик болометров на основе тонких пленок YBCO |
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2012 |
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ЖТФ |
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ЖТФ |
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82 |
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12 |
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108-111 |
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YBCO HEB NEP |
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Представлены первые результаты измерения болометрического отклика высокотемпературных сверхпроводниковых детекторов на основе тонких пленок YBCO на электромагнитное излучение с частотой 2.5 THz. Минимальное значение оптической мощности, эквивалентной шуму созданных детекторов, составило 3.5· 10-9 W/sqrt(Hz)sqrt. Обсуждена возможность дальнейшего увеличения чувствительности исследуемых детекторов. |
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1825 |
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Pekker, David; Shah, Nayana; Sahu, Mitrabhanu; Bezryadin, Alexey; Goldbart, Paul M. |
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Title |
Stochastic dynamics of phase-slip trains and superconductive-resistive switching in current-biased nanowires |
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2009 |
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Phys. Rev. B |
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80 |
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214525 (1 to 17) |
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superconducting nanowire, phase-slip, order parameter, HEB distributed model, HEB model |
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Superconducting nanowires fabricated via carbon-nanotube templating can be used to realize and study quasi-one-dimensional superconductors. However, measurement of the linear resistance of these nanowires have been inconclusive in determining the low-temperature behavior of phase-slip fluctuations, both quantal and thermal. Thus, we are motivated to study the nonlinear current-voltage characteristics in current-biased nanowires and the stochastic dynamics of superconductive-resistive switching, as a way of probing phase-slip events. In particular, we address the question: can a single phase-slip event occurring somewhere along the wire—during which the order-parameter fluctuates to zero—induce switching, via the local heating it causes? We explore this and related issues by constructing a stochastic model for the time evolution of the temperature in a nanowire whose ends are maintained at a fixed temperature. We derive the corresponding master equation as a tool for evaluating and analyzing the mean switching time at a given value of current (smaller than the depairing critical current). The model indicates that although, in general, several phase-slip events are necessary to induce switching via a thermal runaway, there is indeed a regime of temperatures and currents in which a single event is sufficient. We carry out a detailed comparison of the results of the model with experimental measurements of the distribution of switching currents, and provide an explanation for the rather counterintuitive broadening of the distribution width that is observed upon lowering the temperature. Moreover, we identify a regime in which the experiments are probing individual phase-slip events, and thus offer a way of unearthing and exploring the physics of nanoscale quantum tunneling of the one-dimensional collective quantum field associated with the superconducting order parameter. |
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Recommended by Klapwijk |
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923 |
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