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Pekker, David; Shah, Nayana; Sahu, Mitrabhanu; Bezryadin, Alexey; Goldbart, Paul M. |
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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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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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Recommended by Klapwijk |
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923 |
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Sahu, Mitrabhanu; Bae, Myung-Ho; Rogachev, Andrey; Pekker, David; Wei, Tzu-Chieh; Shah, Nayana; Goldbart, Paul M.; Bezryadin, Alexey |
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Title |
Individual topological tunnelling events of a quantum field probed through their macroscopic consequences |
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2009 |
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Nature Phys. |
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Nature Phys. |
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5 |
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503-508 |
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phase slips, superconducting nanowires |
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Phase slips are topological fluctuations that carry the superconducting order-parameter field between distinct current-carrying states. Owing to these phase slips, superconducting nanowires acquire electrical resistance. In such wires, it is well known that at higher temperatures phase slips occur through the process of thermal barrier-crossing by the order-parameter field. At low temperatures, the general expectation is that phase slips should proceed through quantum tunnelling events, which are known as quantum phase slips. However, resistive measurements have produced evidence both for and against the occurrence of quantum phase slips. Here, we report evidence for the observation of individual quantum phase-slip events in homogeneous ultranarrow wires at high bias currents. We accomplish this through measurements of the distribution of switching currents for which the width exhibits a rather counter-intuitive, monotonic increase with decreasing temperature. Importantly, measurements show that in nanowires with larger critical currents, quantum fluctuations dominate thermal fluctuations up to higher temperatures. |
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Recommended by Klapwijk |
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928 |
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Ovchinnikov, Yu. N.; Varlamov, A. A. |
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Fluctuation-dissipative phenomena in a narrow superconducting channel carrying current below critical |
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2009 |
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arXiv |
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0910.2659v1 |
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1-4 |
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superconducting nanowire, resistance calculation |
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The theory of current transport in a narrow superconducting channel accounting for thermal fluctuations is developed. These fluctuations result in the appearance of small but finite dissipation in the sample. The value of corresponding voltage is found as the function of temperature (close to transition temperature) and arbitrary bias current. It is demonstrated that the value of the activation energy (exponential factor in the Arrenius law) when current approaches to the critical one is proportional to (1-J/Jc)^(5/4). This result is in concordance with the one for the affine phenomenon of the Josephson current decay due to the thermal phase fluctuations, where the activation energy proportional (1-J/J_c)^(3/2)(the difference in the exponents is related to the additional current dependence of the order parameter). Found dependence of the activation energy on current explains the enormous discrepancy between the theoretically predicted before and the experimentally observed broadening of the resistive transition. |
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arXiv:0910.2659v1; 4 pages, 3 figures |
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931 |
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Khosropanah P.; Baryshev A.; Zhang W.; Jellema W.; Hovenier J.N.; Gao G.R.; Klapwijk T.M; Paveliev D.G.; Williams B.S.; Kumar S.; Hu Q.; Reno J.L.; Klein B.; Hesler J.L. |
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Phase-locking of a 2.7-THz quantum cascade laser to a microwave reference |
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2009 |
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Optics Letters |
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34 |
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2958-2960 |
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We demonstrate the phase locking of a 2.7 THz metal–metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier chain (X12) from a
microwave synthesizer at ~ 15 GHz. Both laser and reference radiations are coupled into a bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. The spectral analysis of the beat signal con-firms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range. |
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RPLAB @ atomics90 @ |
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966 |
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Ozhegov, R. V.; Smirnov, A. V.; Vakhtomin, Yu. B.; Smirnov, K. V.; Divochiy, A. V.; Goltsman, G. N. |
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Ultrafast superconducting bolometer receivers for terahertz applications |
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2009 |
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Proc. PIERS |
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Proc. PIERS |
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867 |
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HEB |
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The research by the group of Moscow State Pedagogical University into the hot-electron phenomena in thin superconducting films has led to the development of new types of detectors and their use both in fundamental and applied studies. In this paper, we present the results of testing the terahertz HEB receiver systems based on ultrathin (∼ 4 nm) NbN and MoRe detectors with a response time of 50 ps and 1 ns, respectively. We have developed three types of devices which differ in the way a terahertz signal is coupled to the detector and cover the following ranges: 0.3–3 THz, 0.1–30 THz and 25–70 THz. In the case of the receiving system optimized for 0.3–3 THz, the sensitive element (a strip of asuperconductor with planar dimensions of 0.2μm (length) by 1.7μm (width)) was integrated witha planar broadband log-spiral antenna. For additional focusing ofthe incident radiation a silicon hyperhemispherical lens was used. For the 0.1–30 THz receivingsystem, the sensitive element was patterned as parallel strips(2μm wide each) filling an area of 500×500μm2with a filling factor of 0.5. In the receivingsystem of this type we used direct coupling of the incident radiation to the sensitive element. Inthe 25–70 THz range (detector type 2/2a in Table 1) we used a square-shaped superconductingdetector with planar dimensions of 10×10μm2. Incident radiation was coupled to the detectorwith the use of a germanium hyperhemispherical lens.The response time of the above receiving systems is determined by the cooling rate of the hotelectrons in the film. That depends on the electron-phonon interaction time, which is less forultrathin NbN than in MoRe. |
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Moscow, Russia |
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The Electromagnetics Academy |
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777 Concord Avenue, Suite 207 Cambridge, MA 02138 |
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1559-9450 |
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978-1-934142-09-7 |
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RPLAB @ sasha @ ozhegovultrafast |
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1022 |
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