Supercurrent-Induced Temperature Gradient across a Nonequilibrium SNS Josephson Junction

Crosser, Michael S.; Virtanen, Pauli; Heikkilä, Tero T.; Birge, Norman O.

doi:10.1103/physrevlett.96.167004

Cited by 12 publications

(9 citation statements)

References 24 publications

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“…The discussion provides information that was not included in our previous report on this experiment. 12 Together these experiments demonstrate the richness of phenomena present in S/N/S Josephson junctions under nonequilibrium conditions.…”

Section: Introductionmentioning

confidence: 70%

Nonequilibrium transport in mesoscopic multi-terminal SNS Josephson junctions

et al. 2008

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We report the results of several nonequilibrium experiments performed on superconducting/normal/superconducting (S/N/S) Josephson junctions containing either one or two extra terminals that connect to normal reservoirs. Currents injected into the junctions from the normal reservoirs induce changes in the electron energy distribution function, which can change the properties of the junction. A simple experiment performed on a 3-terminal sample demonstrates that quasiparticle current and supercurrent can coexist in the normal region of the S/N/S junction. When larger voltages are applied to the normal reservoir, the sign of the current-phase relation of the junction can be reversed, creating a "π-junction." We compare quantitatively the maximum critical currents obtained in 4-terminal π-junctions when the voltages on the normal reservoirs have the same or opposite sign with respect to the superconductors. We discuss the challenges involved in creating a "Zeeman" π-junction with a parallel applied magnetic field and show in detail how the orbital effect suppresses the critical current. Finally, when normal current and supercurrent are simultaneously present in the junction, the distribution function develops a spatially inhomogeneous component that can be interpreted as an effective temperature gradient across the junction, with a sign that is controllable by the supercurrent. Taken as a whole, these experiments illustrate the richness and complexity of S/N/S Josephson junctions in nonequilibrium situations. PACS numbers: 74.50.+r, 85.25.Am, 85.25.Cp

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Section: Introductionmentioning

confidence: 70%

Nonequilibrium transport in mesoscopic multi-terminal SNS Josephson junctions

et al. 2008

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“…Away from linear response, a nonequilibrium modification of the distribution function f due to the mixing 23 has also been experimentally observed in Ref. 24.…”

Section: Figmentioning

confidence: 91%

Peltier effects in Andreev interferometers

Virtanen¹,

Heikkilä²

2007

Phys. Rev. B

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The superconducting proximity effect is known to modify transport properties of hybrid normal--superconducting structures. In addition to changing electrical and thermal transport separately, it alters the thermoelectric effects. Changes to one off-diagonal element $L_{12}$ of the thermoelectric matrix $L$ have previously been studied via the thermopower, but the remaining coefficient $L_{21}$ which is responsible for the Peltier effect has received less attention. We discuss symmetry relations between $L_{21}$ and $L_{12}$ in addition to the Onsager reciprocity, and calculate Peltier coefficients for a specific structure. Similarly as for the thermopower, for finite phase differences of the superconducting order parameter, the proximity effect creates a Peltier effect significantly larger than the one present in purely normal-metal structures. This results from the fact that a nonequilibrium supercurrent carries energy.Comment: 5 pages, 4 figure

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“…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].…”

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confidence: 99%

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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Supercurrent-Induced Temperature Gradient across a Nonequilibrium SNS Josephson Junction

Cited by 12 publications

References 24 publications

Nonequilibrium transport in mesoscopic multi-terminal SNS Josephson junctions

Nonequilibrium transport in mesoscopic multi-terminal SNS Josephson junctions

Peltier effects in Andreev interferometers

Hot-electron effects in InAs nanowire Josephson junctions

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