Dynamics of conversion of supercurrents into normal currents and vice versa

Jacobs, Arne; Kümmel, Reiner

doi:10.1103/physrevb.64.104515

Cited by 10 publications

(7 citation statements)

References 28 publications

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“…The mutual conversion between normal and supercurrent via Andreev reflection [79] affects the QP density: The dissipative normal current is due to a diffusive motion of the QPs and is thus almost proportional to the gradient of their density, J N ∝ ∇n qp . Consequently, the more normal current is converted into supercurrent along the superconductor, the more the QP density gradient decreases.…”

Section: Andreev Reflection and Qp Reductionmentioning

confidence: 99%

Role of the proximity effect for normal-metal quasiparticle traps

Schmit,

Wilhelm

2020

Preprint

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The performance of many superconducting devices is degraded in presence of non-equilibrium quasiparticles in the superconducting part. One promising approach towards their evacuation is the use of normal-metal quasiparticle traps, where normal metal is brought into good metallic contact with the superconductor. A voltage biased normal-metal-insulator-superconductor junction equipped with such a trap is used to investigate on the trapping performance and the part played by the superconducting proximity effect therein. This involves an appropriate one-dimensional model of the junction and the numerical solution of Usadel equations describing the non-equilibrium state of the superconductor. The functionality of the trap is determined by the density of states (DOS) at the tunnel barrier. Herein, the proximity effect leads to two antagonistic characteristics affecting the trapping performance: the beneficial reduction of the DOS at an energy |E | = ∆ BCS versus the contraction of the spectral energy gap causing quasiparticle poisoning. For both effects the trap position is decisive, which needs to be taken into account for optimizing the trapping performance. In addition, the conversion between dissipative normal and supercurrent inside the superconducting part with its impact on the quasiparticle density is studied.

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Section: Andreev Reflection and Qp Reductionmentioning

confidence: 99%

Role of the proximity effect for normal-metal quasiparticle traps

Schmit,

Wilhelm

2020

Preprint

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“…The time-evolution of localized wave-packets scattering across a superconductornormal interface was explored long ago. [26][27][28] More recently the analysis has been extended to scattering states in superconductor-device-normal (S-D-N) junctions using the wide-band-limit (WBL) approximation 29 and in superconductor-device-superconductor (S-D-S) junctions by approximating the leads with finite size reservoirs. 30 However, there has been no attempt to calculate the response of S-D-S junctions to TD applied voltages using truly semi-infinite leads.…”

Section: Introductionmentioning

confidence: 99%

Time-dependent quantum transport with superconducting leads: A discrete-basis Kohn-Sham formulation and propagation scheme

2010

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In this work we put forward an exact one-particle framework to study nanoscale Josephson junctions out of equilibrium and propose a propagation scheme to calculate the time-dependent current in response to an external applied bias. Using a discrete basis set and Peierls phases for the electromagnetic field, we prove that the current and pairing densities in a superconducting system of interacting electrons can be reproduced in a noninteracting Kohn-Sham ͑KS͒ system under the influence of different Peierls phases and of a pairing field. In the special case of normal systems, our result provides a formulation of time-dependent current-densityfunctional theory in tight-binding models. An extended Keldysh formalism for the nonequilibrium NambuGreen's function ͑NEGF͒ is then introduced to calculate the short-and long-time response of the KS system. The equivalence between the NEGF approach and a combination of the static and time-dependent Bogoliubov-de Gennes ͑BdG͒ equations is shown. For systems consisting of a finite region coupled to N superconducting semi-infinite leads, we numerically solve the static BdG equations with a generalized waveguide approach and their time-dependent version with an embedded Crank-Nicholson scheme. To demonstrate the feasibility of the propagation scheme, we study two paradigmatic models, the single-level quantum dot and a tight-binding chain, under dc, ac, and pulse biases. We provide a time-dependent picture of single and multiple Andreev reflections, show that Andreev bound states can be exploited to generate a zero-bias ac current of tunable frequency, and find a long-living resonant effect induced by microwave irradiation of appropriate frequency.

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“…The time-evolution of localized wave-packets scattering across a superconducting-normal (SN) interface was explored long ago [8,9]. More recently the analysis has been extended to scattering states [10,11,12] in standard quantum transport geometries. However, there has been no attempt to calculate the time-dependent response of a superconductor-normal-superconductor (SNS) junction.…”

Section: Introductionmentioning

confidence: 99%

Time-dependent quantum transport with superconducting leads

Stefanucci

Perfetto

Cini

2010

J. Phys.: Conf. Ser.

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We present results on the microscopic dynamics of electrons in nanoscale systems coupled to superconducting leads. By solving the time-dependent Bogoliubov-deGennes equations for the Nambu-Gorkov Keldysh Green's function we are able to calculate the current and the charge density when the system is perturbed by bias voltages. For scattering of electrons across a normal-superconducting surface we provide a time-dependent picture of the Andreev reflections. When the nanoscale system is contacted to two DC biased superconducting leads the amplitude of the current oscillations at even multiple of the bias can be extracted by Fourier transforming the time-dependent results. In the transient regime the dwelling time is inversely proportional to the bias in agreement with the occurrence of multiple Andreev reflections.

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Dynamics of conversion of supercurrents into normal currents and vice versa

Cited by 10 publications

References 28 publications

Role of the proximity effect for normal-metal quasiparticle traps

Role of the proximity effect for normal-metal quasiparticle traps

Time-dependent quantum transport with superconducting leads: A discrete-basis Kohn-Sham formulation and propagation scheme

Time-dependent quantum transport with superconducting leads

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