Josephson supercurrent in Nb/InN-nanowire/Nb junctions

Frielinghaus, Robert; Batov, I. E.; Weides, Martin; Kohlstedt, H.; Calarco, Raffaella; Schaepers, Th.

doi:10.1063/1.3377897

Cited by 36 publications

(46 citation statements)

References 28 publications

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“…Magnetic depairing -Field-induced depairing suppresses both superconductivity in the S-sections and proximity superconductivity in the N -section 13,14 . For a type-II superconductor with a relatively large gap such as Nb, we can assume depairing in the N -section should dominate.…”

Section: Discussionmentioning

confidence: 99%

“…the narrow junction limit, this becomes a quasi-Gaussian, monotonic decay of the critical current 7,10,11 . Recently, attention has been given to nanoscale, quasi one-dimensional (1D) SN S junctions, such as those readily engineered by contacting semiconductor nanowires with superconducting leads [12][13][14][15][16] . Gating the semiconducting N -section allows for modulating the supercurrent by controlling the chemical potential 12,15 .…”

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Orbital Josephson interference in a nanowire proximity-effect junction

Gharavi

Baugh

2015

Phys. Rev. B

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A semiconductor nanowire based superconductor-normal-superconductor (SN S) junction is modeled theoretically. A magnetic field is applied along the nanowire axis, parallel to the current. The Bogoliubov-de Gennes equations for Andreev bound states are solved while considering the electronic subbands due to radial confinement in the N -section. The energy-versus-phase curves of the Andreev bound states shift in phase as the N -section quasiparticles with orbital angular momentum couple to the axial field. A similar phase shift is observed in the continuum current of the junction. The quantum mechanical result is shown to reduce to an intuitive, semi-classical model when the Andreev approximation holds. Numerical calculations of the critical current versus axial field reveal flux-aperiodic oscillations that we identify as a novel form of Josephson interference due to this orbital subband effect. This behavior is studied as a function of junction length and chemical potential. Finally, we discuss extensions to the model that may be useful for describing realistic devices.The Josephson effect is characterized by a currentphase relationship (CPR) linking macroscopic current flow to the phase gradient of the superconducting order parameter1 . The precise form of the CPR for a superconducting weak link depends on intrinsic factors such as junction geometry, material properties, coherence lengths, etc., in addition to extrinsic variables like temperature and magnetic field. In superconductor-normalsuperconductor (SN S) junctions in which the N -section is long enough to suppress direct tunnelling of Cooper pairs, but shorter than the N -section phase coherence length, a supercurrent may be carried by quasiparticles undergoing Andreev reflection at the S-N interfaces 2-5 . Planar SN S junctions of width large compared to the S-section superconducting coherence length have been studied in great detail 6 (width refers to the dimension perpendicular to the current). These have revealed, for example, Fraunhofer oscillations of the critical current I c with respect to an externally applied out-of-plane magnetic field 7-9 . For junction widths comparable to the S-section coherence length, i.e. the narrow junction limit, this becomes a quasi-Gaussian, monotonic decay of the critical current 7,10,11 . Recently, attention has been given to nanoscale, quasi one-dimensional (1D) SN S junctions, such as those readily engineered by contacting semiconductor nanowires with superconducting leads [12][13][14][15][16] . Gating the semiconducting N -section allows for modulating the supercurrent by controlling the chemical potential 12,15 . The oscillations of the magnetoresistance of a nanowire SN S junction in the voltage-biased state (i.e. no dc supercurrent) versus an axial magnetic field have been studied 16 . Efforts to realize Majorana fermion quasiparticles in 1D semiconductors with strong spin-orbit interaction and proximity coupling to a superconductor 17-20 have further raised interest in this type of junction. Theoretical resul...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Orbital Josephson interference in a nanowire proximity-effect junction

Gharavi

Baugh

2015

Phys. Rev. B

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“…Josephson junctions and coherent quantum transport have been attracting interest in recent years due to the development of modern nanofabrication techniques, which enable the fabrication of nanoscale hybrid superconducting devices in a broad range of design and materials. Josephson junctions realized with semiconductor nanowires (NWs) [4][5][6][7][8][9][10] have shown a high potential in different types of nanoscale devices demonstrating, for example, tunable supercurrents [5,6], the supercurrent reversal [8], and the suppression of supercurrent by hot electron injection [10]. NWs have also been used for superconducting quantum interference devices (SQUIDs) [8] and tunable Cooper pair splitters [11].…”

Section: Introductionmentioning

confidence: 99%

Pb/InAs Nanowire Josephson Junction with High Critical Current and Magnetic Flux Focusing

et al. 2015

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We have studied mesoscopic Josephson junctions formed by highly n-doped InAs nanowires and superconducting Ti/Pb source and drain leads. The current-voltage properties of the system are investigated by varying temperature and external out-of-plane magnetic field. Superconductivity in the Pb electrodes persists up to ∼ 7 K and with magnetic field values up to 0.4 T. Josephson coupling at zero backgate voltage is observed up to 4.5 K and the critical current is measured to be as high as 615 nA. The supercurrent suppression as a function of the magnetic field reveals a diffraction pattern that is explained by a strong magnetic flux focusing provided by the superconducting electrodes forming the junction.

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“…This proximity effect [1,2] modifies the system transport properties and can lead to supercurrent flow in SNS junctions [3]. Recent experimental works showed the potential of semiconductor nanowires (NWs) as building blocks for nanometre-scale devices [4][5][6][7], also in combination with superconducting elements [8][9][10][11][12]. Here, we demonstrate an InAs NW Josephson transistor where supercurrent is controlled by hot-quasiparticle injection from normal-metal electrodes.…”

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Hot-electron effects in InAs nanowire Josephson junctions

et al. 2010

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At a superconductor (S)-normal metal (N) junction pairing correlations can "leak-out" into the N region. This proximity effect [1,2] modifies the system transport properties and can lead to supercurrent flow in SNS junctions [3]. Recent experimental works showed the potential of semiconductor nanowires (NWs) as building blocks for nanometre-scale devices [4][5][6][7], also in combination with superconducting elements [8][9][10][11][12]. Here, we demonstrate an InAs NW Josephson transistor where supercurrent is controlled by hot-quasiparticle injection from normal-metal electrodes. Operational principle is based on the modification of NW electron-energy distribution [13][14][15][16][17][18][19][20] that can yield reduced dissipation and high-switching speed. We shall argue that exploitation of this principle with heterostructured semiconductor NWs opens the way to a host of out-of-equilibrium hybrid-nanodevice concepts [7,21].One practical implementation of the present InAs-NW hot-electron Josephson transistor concept is shown in Figure 1a. The SNS junction was fabricated by e-beam lithography starting from an n-doped InAs NW (the N region, for further details see Methods) and comprises two Ti/Al superconducting electrodes placed at a distance L ≃ 60 nm (S regions). Control electrodes were fabricated by depositing two additional normal-metal Ti/Au leads at the two ends of the NW. As schematically illustrated by the overlay of Fig. 1a, the N leads are used to drive a dissipative current through the NW thereby tuning Josephson coupling in the S-NW-S structure. Figure 2a shows a set of typical IV characteristics from one of the measured S-NW-S junctions at equilibrium (i.e., V inj = 0) and at different bath temperatures T . High critical currents up to I c ≃ 350 nA (corresponding to a supercurrent density ∼ 5.5 kA/cm 2 ) are observed and Josephson coupling typically persists up to about 1 K. Furthermore, from the junction differentialresistance spectra (see Supplementary Materials) we infer a superconducting order parameter ∆ = 120 µeV and a junction normal-state resistance R N ≃ 210 Ω. The I c R N product attains values as large as ≃ 75 µeV and indicates the overall success of our junction-fabrication procedure [22]. Based on carrier-density and electronmobility values (see Methods) we estimate a momentumrelaxation length ℓ ≃ 20 nm and a diffusion coefficient D = 0.02 m 2 /s. Given the junctions geometrical length L we can estimate the Thouless-energy value, i.e., the characteristic energy scale of the N region, E Th = D/L 2 ≃ 4 meV. These values indicate that our devices can be described within the frame of the diffusive short-junction limit (L > ℓ and ∆ ≪ E Th ) [22]. Figure 2b shows the evolution of I c versus T at V inj = 0 for two representative devices D1 and D2. For comparison, the theoretical prediction for an ideal short diffusive SNS junction [22,23] is also plotted assuming for both devices a supercurrent suppression of the order of 45%. Such a suppression can be expected and probably mainly stems from a...

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Josephson supercurrent in Nb/InN-nanowire/Nb junctions

Cited by 36 publications

References 28 publications

Orbital Josephson interference in a nanowire proximity-effect junction

Orbital Josephson interference in a nanowire proximity-effect junction

Pb/InAs Nanowire Josephson Junction with High Critical Current and Magnetic Flux Focusing

Hot-electron effects in InAs nanowire Josephson junctions

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