Double-barrier junction based dc SQUID

Bartolomé, Elena; Brinkman, Alexander; Flokstra, Jakob; Golubov, A. A.; Rogalla, Horst

doi:10.1016/s0921-4534(00)00837-6

Cited by 8 publications

(6 citation statements)

References 13 publications

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“…10,11 A similar feature, and in the same voltage region, was later reported by Bartolome et al 18 It was suggested that the feature is related to phase-coherent transport; specifically, it may be the first direct observation of a resonant dc supercurrent carried by an ABS. 11 An important test of the ABS origin of this feature is provided by its response to a magnetic field H. In a recent work, we reported on a measurement of the magnetic-field dependence of the height of the step, I c (1) , with improved resolution, 13 so that comparison with the theory could be made more reliably.…”

Section: Introductionsupporting

confidence: 77%

Manifestation of coherent effects in the conductivity of superconductor/insulator/normal-metal/insulator/superconductor junctions

2003

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An experimental and theoretical study is presented of coherent effects in electron transport in the doublebarrier SINIS junctions ͑where S, I, and N denote a superconductor, insulator, and normal metal, respectively͒. The appearance of a steplike subgap structure in the current-voltage characteristics of the Nb/Al/AlO x /Al/AlO x /Al/Nb superconducting junctions at a voltage Vϳ⌬ Nb /e ͑where ⌬ Nb is the superconducting energy gap of Nb͒ is interpreted as a manifestation of a nonequilibrium supercurrent at finite dc bias voltage ͑Finite-Bias Josephson Effect͒. The origin of this effect lies in the energy-band structure associated with a set of macroscopic quantum states characteristic of a SINIS junction. Specifically, the junction can have an energy level near energy ⌬ Nb , which provides an additional channel for dc Josephson current at V ϳ⌬ Nb /e. In addition, sharp features in the conductivity at a voltage near the gap-sum voltage were observed in both SINIS and SINININIS junctions, implying correlated quasiparticle tunneling in multiple-barrier junctions. Our theoretical model provides a good qualitative description of the quasiparticle conductivity, including narrow peaks at finite voltage and a zero-voltage anomaly observed on some samples, and suggests an alternative explanation of a feature interpreted earlier as gap-difference feature associated with the tunneling extraction of quasiparticles from the middle Al layer.

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Section: Introductionsupporting

confidence: 77%

Manifestation of coherent effects in the conductivity of superconductor/insulator/normal-metal/insulator/superconductor junctions

2003

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“…neglecting contributions of Π P,S to the function K in Eq. (34). As is obvious from this expression, the parameter τ d drops out from I (1) , and we obtain a simple formula…”

Section: Analytical Resultsmentioning

confidence: 81%

“…Such junctions have been developed using Nb/AlO x /Al/AlO x /Nb technology, and they demonstrated rather large values of γ ∼ 10 4 and a pronounced deficit current. [34][35][36] This is precisely the limit of large electron-hole dephasing studied in this paper. In order to investigate a crossover to the regime of small dephasing at γ ∼ 1 one needs to use junctions with more transparent NS interfaces, such as junctions based on diffusive InAs 2D electron gas or graphene, or corresponding nanowires and nanotubes.…”

Section: Discussionmentioning

confidence: 99%

Dissipative charge transport in diffusive superconducting double-barrier junctions

2011

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We solve the coherent multiple Andreev reflection (MAR) problem and calculate current-voltage characteristics (IVCs) for Josephson SINIS junctions, where S are local-equilibrium superconducting reservoirs, I denotes tunnel barriers, and N is a short diffusive normal wire, the length of which is much smaller than the coherence length, and the resistance is much smaller than the resistance of the tunnel barriers. The charge transport regime in such junctions qualitatively depends on a characteristic value γ = τ d ∆ of relative phase shifts between the electrons and retro-reflected holes accumulated during the dwell time τ d . In the limit of small electron-hole dephasing γ ≪ 1, our solution recovers a known formula for a short mesoscopic connector extended to the MAR regime. At large dephasing, the subharmonic gap structure in the IVC scales with γ −1 , which thus plays the role of an effective tunneling parameter. In this limit, the even gap subharmonics are resonantly enhanced, and the IVC exhibits portions with negative differential resistance.

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“…From resonances in the SQUID washer, C was determined to be 0.015 pF/µm 2 , corresponding to the capacitance of two SIS junctions in series. 58 It is assumed that this value is only weakly depending on the transparency of the barrier. The dependence of I c and R N on the junction parameters, such as γ eff , follow from the modeling of the stationary properties in Ref.…”

Section: Application: the Nature Of The Intrinsic Shuntmentioning

confidence: 99%

Microscopic nonequilibrium theory of double-barrier Josephson junctions

et al. 2003

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We study nonequilibrium charge transport in a double-barrier Josephson junction, including nonstationary phenomena, using the time-dependent quasiclassical Keldysh Green's function formalism. We supplement the kinetic equations by appropriate time-dependent boundary conditions and solve the time-dependent problem in a number of regimes. From the solutions, current-voltage characteristics are derived. It is understood why the quasiparticle current can show excess current as well as deficit current and how the subgap conductance behaves as function of junction parameters. A time-dependent nonequilibrium contribution to the distribution function is found to cause a nonzero averaged supercurrent even in the presence of an applied voltage. Energy relaxation due to inelastic scattering in the interlayer has a prominent role in determining the transport properties of double-barrier junctions. Actual inelastic scattering parameters are derived from experiments. It is shown as an application of the microscopic model, how the nature of the intrinsic shunt in double-barrier junctions can be explained in terms of energy relaxation and the opening of Andreev channels.

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Double-barrier junction based dc SQUID

Cited by 8 publications

References 13 publications

Manifestation of coherent effects in the conductivity of superconductor/insulator/normal-metal/insulator/superconductor junctions

Manifestation of coherent effects in the conductivity of superconductor/insulator/normal-metal/insulator/superconductor junctions

Dissipative charge transport in diffusive superconducting double-barrier junctions

Microscopic nonequilibrium theory of double-barrier Josephson junctions

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