Manipulation and Generation of Supercurrent in Out-of-Equilibrium Josephson Tunnel Nanojunctions

Tirelli, Stefano; Savin, A. M.; García, César Pascual; Pekola, Jukka P.; Beltram, Fabio; Giazotto, Francesco

doi:10.1103/physrevlett.101.077004

Cited by 37 publications

(49 citation statements)

References 24 publications

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“…The adoption of self-assembled nanostructures as the core element of this class of devices thus paves the way to rather broad opportunities since it allows the design and growth of epitaxial quantum systems characterized by atomically-defined potential profiles [6,30], a crucial element for several innovative outof-equilibrium nanodevice schemes [7,20,21].…”

Section: As a Thermometer We Extract The Electron Temperature Te As mentioning

confidence: 99%

“…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%

“…sured temperature-calibration data in Fig. 2b, i.e., by exploiting the equilibrium Josephson junction as an electron thermometer [17,20,29].…”

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confidence: 99%

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Hot-electron effects in InAs nanowire Josephson junctions

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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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Section: As a Thermometer We Extract The Electron Temperature Te As mentioning

confidence: 99%

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Hot-electron effects in InAs nanowire Josephson junctions

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“…The NIS junctions are used to heat selectively the S L or S R electrode as well as to perform accurate electron thermometry [37]. Therefore, instead of varying the exchange field in the Josephson weak link, one could now hold one of the junction electrodes at a fixed temperature and vary the temperature of the other lead while recording the current versus voltage characteristics under conditions of a temperature bias [38][39][40][41][42]. In this context, the electric current can be led through the whole structure via suitable outer superconducting electrodes allowing good electric contact, but providing the required thermal insulation necessary for thermally biasing the Josephson junction.…”

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Manifestation of a spin-splitting field in a thermally biased Josephson junction

Bergeret

Giazotto²

2014

Phys. Rev. B

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We investigate the behavior of a Josephson junction consisting of a ferromagnetic insulator-superconductor (FI-S) bilayer tunnel coupled to a superconducting electrode. We show that the Josephson coupling in the structure is strengthened by the presence of the spin-splitting field induced in the FI-S bilayer. Such strengthening manifests itself as an increase of the critical current I c with the amplitude of the exchange field. Furthermore, the effect can be strongly enhanced if the junction is taken out of equilibrium by a temperature bias. We propose a realistic setup to assess experimentally the magnitude of the induced exchange field, and predict a drastic deviation of the I c (T ) curve (T is the temperature) with respect to equilibrium. The interplay between superconductivity and ferromagnetism in superconductor-ferromagnet (S-F) hybrids exhibits a large variety of effects studied along the last years [1,2]. Experimental research mainly focuses on the control of the 0-π transition in the S-F-S junctions [3,4] (S-F-S) and on the creation, detection, and manipulation of triplet correlations in S-F hybrids [5][6][7][8][9]. From a fundamental point of view, the key phenomenon for the understanding of these effects is the proximity effect in S-F hybrids, and how the interplay between superconducting and magnetic correlations affect their thermodynamic and transport properties.While most of the theoretical and experimental investigations on S-F structures deal mainly with the penetration of the superconducting order into the ferromagnetic regions, it is also widely known that magnetic correlations can be induced in the superconductor via the inverse proximity effect [10][11][12][13]. If the ferromagnet is an insulator (FI), on the one hand, superconducting correlations are weakly suppressed at the FI-S interface and a finite exchange field, with an amplitude smaller than the superconducting gap 0 , is induced at the interface. Such exchange correlations penetrate into the bulk of S over distances of the order of the coherence length [10]. This results in a splitting of the density of states (DOS) of the superconductor, as observed in a number of experiments [14][15][16][17]. Yet, the spin-split DOS of a superconductor may lead to interesting effects such as, for instance, the absolute spinvalve effect [18][19][20], the magnetothermal Josephson valve [21,22], and the large enhancement of the Josephson coupling observed in F-S-I-S-F junctions (I stands for a conventional insulator) when the magnetic configuration of the F layers is arranged in the antiparallel state [23][24][25][26].In this paper, we show that an enhancement of the Josephson effect between two tunnel-coupled superconductors S L and S R can also be achieved if a unique FI is attached to one of the S electrodes, for instance, the left lead, as shown schematically in Fig. 1(a). According to the discussion above, the presence of the FI splits the DOS in the left superconductor. In principle, the presence of the spin-splitting field causes * sebastian_...

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“…Finally, the strong dependence of the Josephson supercurrent on temperature can be exploited for the realization of controllable thermal Josephson junctions of different kinds. 27,[59][60][61][62] …”

Section: Discussionmentioning

confidence: 99%

Phase-dependent heat transport through magnetic Josephson tunnel junctions

Bergeret

Giazotto²

2013

Phys. Rev. B

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We present an exhaustive study of the coherent heat transport through superconductor-ferromagnet (SF) Josephson junctions including a spin-filter (I sf ) tunneling barrier. By using the quasiclassical Keldysh Green's function technique we derive a general expression for the heat current flowing through a SF-I sf -FS junction and analyze the dependence of the thermal conductance on the spin-filter efficiency, the phase difference between the superconductors and the magnetization direction of the ferromagnetic layers. In the case of noncollinear magnetizations we show explicitly the contributions to the heat current stemming from the singlet and triplet components of the superconducting condensate. We also demonstrate that the magnetothermal resistance ratio of a SF-I sf -FS heat valve can be increased by the spin-filter effect under suitable conditions.

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Manipulation and Generation of Supercurrent in Out-of-Equilibrium Josephson Tunnel Nanojunctions

Cited by 37 publications

References 24 publications

Hot-electron effects in InAs nanowire Josephson junctions

Hot-electron effects in InAs nanowire Josephson junctions

Manifestation of a spin-splitting field in a thermally biased Josephson junction

Phase-dependent heat transport through magnetic Josephson tunnel junctions

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