Charge imbalance in superconductors in the low-temperature limit

Hübler, F.; Lemyre, Julien Camirand; Beckmann, D.; Löhneysen, H. v.

doi:10.1103/physrevb.81.184524

Cited by 67 publications

(101 citation statements)

References 56 publications

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“…An exponential decay of charge imbalance at low temperatures was also found experimentally [23]. Therefore, it is quite reliable to extract λ Q * from the experimental data according to Eq.…”

Section: Model Of a Josephson Sns Junction In The Case Of Quasi-mentioning

confidence: 59%

“…(8) [23]. Furthermore, the quasiparticle transmission coefficient β at the injector/superconductor interface was estimated using the values of λ Q * for each sample and Eq.…”

Section: Resultsmentioning

confidence: 99%

“…It is not very obvious for the moment that the proposed method of the λ Q * measurement has clear advantages over the technique used in Refs. [5,23] because it may well be that it also requires corrections related to a difference between coefficients β L and β R due to different voltages at the left and right N/S interfaces. Nevertheless, our experiment and model calculation give a description for real modern submicron Josephson circuits where nonequilibrium effects are undesirable or, on the contrary, can be used to tune Josephson junction characteristics.…”

Section: Resultsmentioning

confidence: 99%

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Nonlocal supercurrent in mesoscopic multiterminal SNS Josephson junction in the low-temperature limit

et al. 2014

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A nonlocal supercurrent was observed in mesoscopic planar SNS Josephson junctions with additional normal-metal electrodes, where nonequilibrium quasiparticles were injected from a normal metal electrode into one of the superconducting banks of the Josephson junction in the absence of a net transport current through the junction. We claim that the observed effect is due to a supercurrent counterflow, appearing to compensate for the quasiparticle flow in the SNS weak link.We have measured the responses of SNS junctions for different distances between the quasiparticle injector and the SNS junction at temperatures far below the superconducting transition temperature. The charge-imbalance relaxation length was estimated by using a modified Kadin, Smith, and Skocpol scheme in the case of a planar geometry. The model developed allows us to describe the interplay of charge imbalance and Josephson effects in the nanoscale proximity system in detail.

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Section: Model Of a Josephson Sns Junction In The Case Of Quasi-mentioning

confidence: 59%

“…(8) [23]. Furthermore, the quasiparticle transmission coefficient β at the injector/superconductor interface was estimated using the values of λ Q * for each sample and Eq.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Nonlocal supercurrent in mesoscopic multiterminal SNS Josephson junction in the low-temperature limit

et al. 2014

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“…Namely, the charge transfer asymmetry gives rise to the buildup of a non-equilibrium quasiparticle charge density ρ. This charge imbalance can be measured with a normalmetal voltage probe attached to the superconductor: the method proposed in [23] and widely applied in recent years [24,25], see Fig. 4.…”

Section: −1mentioning

confidence: 99%

Control of Andreev bound state population and related charge-imbalance effect

Riwar

Houzet

Meyer

et al. 2015

J. Phys.: Condens. Matter

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Motivated by recent experimental research, we study the processes in an ac driven superconducting constriction whereby one quasiparticle is promoted to the delocalized states outside the superconducting gap. We demonstrate that with these processes one can control the population of the Andreev bound states in the constriction. We stress an interesting charge asymmetry of these processes that may produce a charge imbalance of accumulated quasiparticles, which depends on the phase.PACS numbers: 74.40. Gh., 74.50.+r, 74.78.Na Superconducting nanodevices are among the most promising candidates to realize quantum computation in the solid state [1], and for many other applications. Quasiparticle poisoning, whereby an unwanted quasiparticle enters a bound state in the device, is an important factor harming their proper operation [2]. Naively, the superconducting gap ∆ should ensure an exponentially small quasiparticle concentration at low temperatures. However, various experiments indicate that a long-lived, non-equilibrium quasiparticle population persists in the superconductor, affecting the operation of various superconducting devices [3][4][5][6][7][8], including tempting proposals to use Majorana states in superconductors [9][10][11].This makes it important to develop the means of an active control of the quasiparticle population in bound states associated with a nano-device.As a generic model we consider a superconducting constriction with a few highly transparent channels. Such constrictions are made on the basis of atomic break junctions [12]. The simplicity of their theoretical description enabled detailed theoretical research [13][14][15]. In the presence of a phase difference at the constriction, an Andreev bound state (ABS) is formed in each channel [16,17]. In a recent pioneering experiment [18], the population of such a single bound state has been detected by its effect on the supercurrent in the constriction. The spectroscopy of Andreev states has also been successfully performed in this setup [19,20]. Thus motivated, we theoretically investigate the control of the population of quasiparticles in the ABS at a superconducting constriction by means of pulses of high-frequency microwave irradiation.In this Letter, we demonstrate that an efficient control of the ABS can be achieved by inducing the processes of ionization and refill (Fig. 1), due to an ac modulation of the phase drop across the junction, φ(t) = φ+δφ sin(Ωt). In the course of such a process, a quasiparticle is promoted to the delocalized states and leaves the constriction. We compute the rates of these processes in the lowest order in irradiation amplitude δφ. We find an interesting charge asymmetry of the emitted quasiparticles. This asymmetry leads to a net quasiparticle current and charge imbalance of the quasiparticles accumulated in the vicinity of the constriction. Charge imbalance can be measured by a standard setup using a normalsuperconducting (N-S) tunnel junction [21][22][23][24][25].We focus on the regime of low temperatures whi...

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“…Such a charge imbalance can be measured by the standard setup of a normal metalsuperconducting (N-S) contact [31][32][33], by use of which the decay of the nonequilibrium charge was investigated experimentally [34,35]. Either the quasiparticle current eq is collected by a sufficiently conducting normal metal contact in the vicinity of the superconducting junction or the N-S contact is used to measure the voltage signal due to the nonequilibrium charge accumulation.…”

Section: Introductionmentioning

confidence: 99%

Strong effects of weak ac driving in short superconducting junctions

et al. 2015

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We study a short multichannel superconducting junction subject to dc and ac phase biases. The ac modulation changes the occupation of the Andreev bound states formed at the constriction by transitions between bound states and the continuum. In a short junction, the nonequilibrium Andreev bound-state population may relax through processes that conserve parity of the occupation number on the same bound state and processes that do not conserve it. We argue that the parity-conserving processes occur on a much faster time scale. In this case, even a weak driving may lead to a large nonequilibrium quasiparticle population scaling with the number of channels and results in a large deviation of the supercurrent from its equilibrium value. We show that this effect is accompanied by a quasiparticle current which may lead to a measurable charge imbalance in the vicinity of the junction. Furthermore, we study the time evolution of the supercurrent after switching off the ac drive. On a time scale where parity relaxation is negligible, the supercurrent relaxes to a stationary nonequilibrium state. Finally, we briefly outline the regime of ultraweak driving where the ac-induced processes occur on a time scale comparable to that of parity relaxation.

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Charge imbalance in superconductors in the low-temperature limit

Cited by 67 publications

References 56 publications

Nonlocal supercurrent in mesoscopic multiterminal SNS Josephson junction in the low-temperature limit

Nonlocal supercurrent in mesoscopic multiterminal SNS Josephson junction in the low-temperature limit

Control of Andreev bound state population and related charge-imbalance effect

Strong effects of weak ac driving in short superconducting junctions

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