Dissipative charge transport in diffusive superconducting double-barrier junctions

Bezuglyĭ, E. V.; Bratus, E. N.; Shumeiko, Vitaly

doi:10.1103/physrevb.83.184517

Cited by 9 publications

(27 citation statements)

References 38 publications

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“…The stars and crosses are the experimental data from Table I; as can be seen, the most devices are in the intermediate limit where E Th ≈ . also found, experimentally and theoretically, in ballistic 2DEG InAs [27], and computed for fully diffusive junctions [38,39]. In our case, the experimental values fall on curves with a typical effective transparency between 0.2 and 0.4 being only weakly device dependent between batches of nanowires.…”

Section: Excess Currentsupporting

confidence: 72%

“…Ref. [39]). Given such a similarity, we may conclude that although device B 5 has transparent S-NW interfaces, the model [43] might better capture the effect of the junction length.…”

Section: Josephson Currentmentioning

confidence: 99%

“…15, we present a set of IVCs for the suspended device C 12 (L ≈ 200 nm and R n = 3.6 k ) for gate voltages ranging from V g = −2.16 to V g = +0.92 V. At large positive gate voltage, i.e., at large conductance, the IVC shows significant excess current and enhanced subgap conductance, indicating a highly transmissive SNS regime. In the opposite limit of large negative gate voltage (small conductance), the IVC has a typical form for SIS tunnel junctions with negative excess current [39] and strongly suppressed subgap conductance. The suppression of the subgap conductance is explained by the small probability of MAR processes at small voltage, which scales with D n , where n = 2 /eV is the number of Andreev reflections.…”

Section: Gate Dependencementioning

confidence: 99%

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Charge transport in InAs nanowire Josephson junctions

et al. 2014

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We present an extensive experimental and theoretical study of the proximity effect in InAs nanowires connected to superconducting electrodes. We fabricate and investigate devices with suspended gate-controlled nanowires and nonsuspended nanowires, with a broad range of lengths and normal-state resistances. We analyze the main features of the current-voltage characteristics: the Josephson current, excess current, and subgap current as functions of length, temperature, magnetic field, and gate voltage, and compare them with theory. The Josephson critical current for a short-length device, L = 30 nm, exhibits a record high magnitude of 800 nA at low temperature that comes close to the theoretically expected value. The critical current in all other devices is typically reduced compared to the theoretical values. The excess current is consistent with the normal resistance data and agrees well with the theory. The subgap current shows a large number of structures; some of them are identified as subharmonic gap structures generated by multiple Andreev reflection. The other structures, detected in both suspended and nonsuspended devices, have the form of voltage steps at voltages that are independent of either the superconducting gap or length of the wire. By varying the gate voltage in suspended devices, we are able to observe a crossover from typical tunneling transport at large negative gate voltage, with suppressed subgap current and negative excess current, to pronounced proximity junction behavior at large positive gate voltage, with enhanced Josephson current and subgap conductance as well as a large positive excess current.

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Section: Excess Currentsupporting

confidence: 72%

“…Ref. [39]). Given such a similarity, we may conclude that although device B 5 has transparent S-NW interfaces, the model [43] might better capture the effect of the junction length.…”

Section: Josephson Currentmentioning

confidence: 99%

Section: Gate Dependencementioning

confidence: 99%

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Charge transport in InAs nanowire Josephson junctions

et al. 2014

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“…Mesoscopic fluctuations of the DOS [23,24] are small provided G ≫ G Q . It looks like everything is understood, perhaps except a small dip or peak in the DOS just at the gap edge for the diffusive case, which has been seen in [3,5,[25][26][27][28], but never attracted proper attention.In this Letter, we demonstrate that the appearance of a secondary gap, in addition to the well-known gap ∼E Th in the DOS around the Fermi level, is a generic feature of S-N-S structure containing high-transmission S-N contacts. In the case of a chaotic cavity with two identical ballistic contacts, the secondary gap exists for any E Th > 0.68Δ and vanishes as Δ 3 =E…”

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confidence: 99%

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confidence: 99%

“Smile” Gap in the Density of States of a Cavity between Superconductors

et al. 2014

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The density of Andreev levels in a normal metal (N) in contact with two superconductors (S) is known to exhibit an induced minigap related to the inverse dwell time. We predict a small secondary gap just below the superconducting gap edge-a feature that has been overlooked so far in numerous microscopic studies of the density of states in S-N-S structures. In a generic structure with N being a chaotic cavity, the secondary gap is the widest at zero phase bias. It closes at some finite phase bias, forming the shape of a "smile". Asymmetric couplings give even richer gap structures near the phase difference π. All the features found should be amendable to experimental detection in high-resolution low-temperature tunneling spectroscopy. DOI: 10.1103/PhysRevLett.112.067001 PACS numbers: 74.45.+c, 74.78.Na The modification of the density of states (DOS) in a normal metal by a superconductor in its proximity was discovered almost 50 years ago [1]. Soon afterwards, it was predicted, theoretically, for diffusive structures that a socalled minigap of the order of the inverse dwell time in the normal metal (or the Thouless energy) appears in the spectrum [2]. The energy-dependent DOS reflects the energy scale of electron-hole decoherence, and is sensitive to the distance, the geometry, and the properties of the contact between the normal metal and the superconductor [3][4][5]. The details of the local density of states in proximity structures have been investigated experimentally many years later [6][7][8][9][10] and the theoretical predictions have been confirmed [11][12][13] Substantial interest has been paid to the density of states in a finite normal metal between two superconducting leads with different superconducting phases [14,15]. The difference between diffusive [5] and classical ballistic [16] dynamics has been investigated [17]. Many publications have addressed the dependence of the minigap on the competition between dwell and Ehrenfest time [18,19]. The most generic model in this context is that of a chaotic cavity, where a piece of normal metal is connected to the superconductors by means of ballistic point contacts that dominate the resistance of the structure in the normal state. The Thouless energy is given by E Th ¼ ðG Σ =G Q Þδ S , G Q ¼ e 2 =πℏ being the conductance quantum, G Σ ≫ G Q being the total conductance of the contacts, and δ S being the level spacing in the normal metal provided the contacts are closed. The DOS in chaotic cavities has been studied for years [19][20][21][22].The DOS depends on the ratio of E Th and the superconducting energy gap Δ, and on the superconducting phase difference. If the dwell time exceeds the Ehrenfest time, qualitative features of the DOS do not seem to depend much on the contact nature and are the same for ballistic, diffusive, and tunnel contacts. Mesoscopic fluctuations of the DOS [23,24] are small provided G ≫ G Q . It looks like everything is understood, perhaps except a small dip or peak in the DOS just at the gap edge for the diffusive case, which has ...

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Current–voltage characteristics of asymmetric double-barrier Josephson junctions

Bezuglyĭ

Bratus

Shumeiko

2014

Physica C: Superconductivity

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We develop a theory for the current-voltage characteristics of diffusive superconductor-normal metal-superconductor Josephson junctions with resistive interfaces and the distance between the electrodes smaller than the superconducting coherence length. The theory allows for a quantitative analytical and numerical analysis in the whole range of the interface transparencies and asymmetry. We focus on the regime of large interface resistance compared to the resistance of the normal region, when the electron-hole dephasing in the normal region is significant and the finite length of the junction plays a role. In the limit of strong asymmetry we find pronounced current structures at the combination subharmonics of ∆ + ∆ g , where ∆ g is the proximity minigap in the normal region, in addition to the subharmonics of the energy gap 2∆ in the electrodes. In the limit of rather transparent interfaces, our theory recovers a known formula for the current in a short mesoscopic connector -a convolution of the current through a single-channel point contact with the transparency distribution for an asymmetric double-barrier potential.

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Dissipative charge transport in diffusive superconducting double-barrier junctions

Cited by 9 publications

References 38 publications

Charge transport in InAs nanowire Josephson junctions

Charge transport in InAs nanowire Josephson junctions

“Smile” Gap in the Density of States of a Cavity between Superconductors

Current–voltage characteristics of asymmetric double-barrier Josephson junctions

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