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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 (down) 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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Call Number Serial 898
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Author Bulaevskii, L. N.; Graf, M. J.; Batista, C. D.; Kogan, V. G.
Title Vortex-induced dissipation in narrow current-biased thin-film superconducting strips Type Journal Article
Year (down) 2011 Publication Phys. Rev. B Abbreviated Journal Phys. Rev. B
Volume 83 Issue 14 Pages 9
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Abstract A vortex crossing a thin-film superconducting strip from one edge to the other, perpendicular to the bias current, is the dominant mechanism of dissipation for films of thickness d on the order of the coherence length ξ and of width w much narrower than the Pearl length Λâ‰<ab>wâ‰<ab>ξ. At high bias currents I*<I<Ic the heat released by the crossing of a single vortex suffices to create a belt-like normal-state region across the strip, resulting in a detectable voltage pulse. Here Ic is the critical current at which the energy barrier vanishes for a single vortex crossing. The belt forms along the vortex path and causes a transition of the entire strip into the normal state. We estimate I* to be roughly Ic/3. Furthermore, we argue that such “hot” vortex crossings are the origin of dark counts in photon detectors, which operate in the regime of metastable superconductivity at currents between I* and Ic. We estimate the rate of vortex crossings and compare it with recent experimental data for dark counts. For currents below I*, that is, in the stable superconducting but resistive regime, we estimate the amplitude and duration of voltage pulses induced by a single vortex crossing.
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Notes SSPD Approved no
Call Number RPLAB @ gujma @ Serial 688
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Author Kerman, Andrew J.; Yang, Joel K. W.; Molnar, Richard J.; Dauler, Eric A.; Berggren, Karl K.
Title Electrothermal feedback in superconducting nanowire single-photon detectors Type Journal Article
Year (down) 2009 Publication Phys. Rev. B Abbreviated Journal Phys. Rev. B
Volume 79 Issue 10 Pages 4
Keywords SNSPD
Abstract We investigate the role of electrothermal feedback in the operation of superconducting nanowire single-photon detectors (SNSPDs). It is found that the desired mode of operation for SNSPDs is only achieved if this feedback is unstable, which happens naturally through the slow electrical response associated with their relatively large kinetic inductance. If this response is sped up in an effort to increase the device count rate, the electrothermal feedback becomes stable and results in an effect known as latching, where the device is locked in a resistive state and can no longer detect photons. We present a set of experiments which elucidate this effect and a simple model which quantitatively explains the results.
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Notes Approved no
Call Number RPLAB @ gujma @ Serial 680
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Author Pekker, David; Shah, Nayana; Sahu, Mitrabhanu; Bezryadin, Alexey; Goldbart, Paul M.
Title Stochastic dynamics of phase-slip trains and superconductive-resistive switching in current-biased nanowires Type Journal Article
Year (down) 2009 Publication Phys. Rev. B Abbreviated Journal
Volume 80 Issue Pages 214525 (1 to 17)
Keywords superconducting nanowire, phase-slip, order parameter, HEB distributed model, HEB model
Abstract 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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Notes Recommended by Klapwijk Approved no
Call Number Serial 923
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Author Huard, B.; Pothier, H.; Esteve, D.; Nagaev, K. E.
Title Electron heating in metallic resistors at sub-Kelvin temperature Type Journal Article
Year (down) 2007 Publication Phys. Rev. B Abbreviated Journal Phys. Rev. B
Volume 76 Issue Pages 165426(1-9)
Keywords electron heating in resistor, HEB distributed model, HEB model, hot electrons
Abstract In the presence of Joule heating, the electronic temperature in a metallic resistor placed at sub-Kelvin temperatures can significantly exceed the phonon temperature. Electron cooling proceeds mainly through two processes: electronic diffusion to and from the connecting wires and electron-phonon coupling. The goal of this paper is to present a general solution of the problem in a form that can easily be used in practical situations. As an application, we compute two quantities that depend on the electronic temperature profile: the second and the third cumulant of the current noise at zero frequency, as a function of the voltage across the resistor. We also consider time-dependent heating, an issue relevant for experiments in which current pulses are used, for instance, in time-resolved calorimetry experiments.
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Notes Recommended by Klapwijk as example for writing the article on the HEB model. Approved no
Call Number Serial 936
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