Frequency-dependent admittance of a short superconducting weak link

Kos, Filip; Nigg, Simon E.; Glazman, L. I.

doi:10.1103/physrevb.87.174521

Cited by 63 publications

(115 citation statements)

References 35 publications

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“…In the present paper we extend our considerations to a short multichannel superconducting junction [2,3] with a conductance G much larger than the conductance quantum G Q = e 2 /π . In this case the ABSs form a quasicontinuous spectrum.…”

Section: Introductionmentioning

confidence: 99%

“…As the ABS supports a supercurrent, it offers the possibility of the direct experimental observation of the bound-state occupation [21]. A nonequilibrium driving of the phase bias [3,[22][23][24][25] was experimentally deployed for the spectroscopy of Andreev levels [26,27].…”

Section: Introductionmentioning

confidence: 99%

“…The ac properties of superconducting junctions have been under extensive scrutiny, both theoretically [1][2][3] and experimentally [4][5][6], due to manifold reasons, such as the possibility of a microwave-induced enhancement of the critical current or generally for the study of high-frequency superconducting circuits.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Strong effects of weak ac driving in short superconducting junctions

et al. 2015

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“…[1,[10][11][12][13][14][15][16] In contrast, the near-equilibrium response of superconductor-normalmetal-superconductor (SNS) junctions to weak microwave radiation has become an active area of investigation only recently. [17][18][19][20][21] While the adiabatic contribution to the kinetic inductance can be calculated from the dc current-phase relation, at high frequencies both reactive and dissipative contributions arise also from other mechanisms, such as driven transitions between quasiparticle states and oscillation of the Andreev level populations. [18] Surprisingly, however, little experimental data has been published on the topic thus far.…”

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confidence: 99%

Microwave Admittance of Gold‐Palladium Nanowires with Proximity‐Induced Superconductivity

Lake

Govenius

Kokkoniemi

et al. 2017

Adv Elect Materials

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measurements. [8,9] Shapiro steps, supercurrent enhancement, and other non-equilibrium effects under intense microwave irradiation have also been extensively studied. [1,[10][11][12][13][14][15][16] In contrast, the near-equilibrium response of superconductor-normalmetal-superconductor (SNS) junctions to weak microwave radiation has become an active area of investigation only recently. [17][18][19][20][21] While the adiabatic contribution to the kinetic inductance can be calculated from the dc current-phase relation, at high frequencies both reactive and dissipative contributions arise also from other mechanisms, such as driven transitions between quasiparticle states and oscillation of the Andreev level populations. [18] Surprisingly, however, little experimental data has been published on the topic thus far. [22,23] The parameter regimes and materials studied in the published experiments are very sparse, hence limiting the extent to which theoretical predictions [17][18][19][20][21] can be tested. In practice, data on the effective inductance and losses also expedites the process of designing high-frequency SNS-junction-based circuits, such as the SNS nanobolometer. [24,25] Previous experimental studies [22,23] have probed flux-and temperature-dependent changes in the linear microwave response of a superconducting ring with a gold normal-metal inclusion. The superconducting ring consisted of ion-beamdeposited tungsten in the first experiments, [22] and sputterdeposited Nb with a thin Pd layer at the SN interface in the later experiments. [23] A single SNS ring was biased with a dc magnetic flux and coupled weakly to a multi-mode microwave resonator. By measuring flux-dependent shifts in the quality factors and resonance frequencies, the authors determined how the complex-valued electrical susceptibility χ changes. [22,23] The change in χ, as a function of flux and temperature, was reported to be in excellent agreement with theoretical predictions based on Usadel equations and numerical simulations. However, the implicit offsets in both the real and imaginary parts of the reported susceptibility prevent a comparison to the theoretically predicted absolute values of Re In this article, we present measurements of the SNS junction admittance Z -1 (ω) = χ/iω for gold-palladium based junctions at angular frequencies ω of order 2π × 1 GHz. We use a chain of

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“…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].…”

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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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Frequency-dependent admittance of a short superconducting weak link

Cited by 63 publications

References 35 publications

Strong effects of weak ac driving in short superconducting junctions

Strong effects of weak ac driving in short superconducting junctions

Microwave Admittance of Gold‐Palladium Nanowires with Proximity‐Induced Superconductivity

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

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