Tunnel spectroscopy of a proximity Josephson junction

Meschke, Matthias; Peltonen, Joonas T.; Pekola, Jukka P.; Giazotto, Francesco

doi:10.1103/physrevb.84.214514

Cited by 42 publications

(73 citation statements)

References 34 publications

(44 reference statements)

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“…According to the above conditions the experimental realization of our thermal nanovalve can be easily achieved with conventional metals and standard lithographic techniques [9][10][11][12] . Superconducting tunnel junctions additionally coupled to the SN ring and the N 1 electrode, serving either as heaters or thermometers, allow to change and monitor the quasiparticle temperature on both sides of the structure 27 .…”

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confidence: 99%

“…Here we propose an alternative approach to control heat transport by envisioning a thermal nanovalve based on proximity effect but phase-controlled by a SQUIPT [9][10][11][12] . Differing from SQUID-based and Andreev interferometers our device allows a drastic quenching of the thermal conductance which makes our proposal an efficient phase-tunable thermal nanovalve.…”

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Proximity nanovalve with large phase-tunable thermal conductance

Strambini

Bergeret

Giazotto

2014

Applied Physics Letters

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We propose a phase-controlled heat-flux quantum valve based on the proximity effect driven by a superconducting quantum interference proximity transistor (SQUIPT). Its operation relies on the phase-dependent quasiparticle density of states in the Josephson weak-link of the SQUIPT which controls thermal transport across the device. In a realistic Al/Cu-based setup the structure can provide efficient control of thermal current inducing temperature swings exceeding ∼ 100 mK, and flux-to-temperature transfer coefficients up to ∼ 500 mK/Φ 0 below 100 mK. The nanovalve performances improve by lowering the bath temperature, making the proposed structure a promising building-block for the implementation of coherent caloritronic devices operating below 1 K.Phase-dependent manipulation of heat in solid-state nanodevices is nowadays one of the major challenges of coherent caloritronics 1 , and plays a key role in determining the physical properties of mesoscopic systems at low temperature. Toward this direction, the prototype for a heat interferometer has been recently realized with a superconducting quantum interference device (SQUID) where the modulation of the thermal current has been achieved thanks to the Josephson coupling 2-5 . Yet, phase-dependent thermal transport has been also demonstrated in Andreev interferometers 6-8 where the proximity effect in a normal metal affects its thermal conductance, and is controlled via a magnetic field.Here we propose an alternative approach to control heat transport by envisioning a thermal nanovalve based on proximity effect but phase-controlled by a SQUIPT 9-12 . Differing from SQUID-based and Andreev interferometers our device allows a drastic quenching of the thermal conductance which makes our proposal an efficient phase-tunable thermal nanovalve. Specifically, we expect an improvement of the temperature swing (up to ∼ 100 mK) and a flux-to-temperature transfer function exceeding 500 mK/Φ 0 at 100 mK.A sketch for the proximity nanovalve is shown in Fig. 1(a) and consists of a SQUIPT composed by a superconducting (S) ring interrupted by a diffusive normal metal (N) wire of length L. We assume the wire transverse dimensions to be negligible in comparison to its length so that it can be considered as quasi-onedimensional. Superconducting correlations are induced in the N wire owing to proximity effect from the S loop a) Electronic

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Proximity nanovalve with large phase-tunable thermal conductance

Strambini

Bergeret

Giazotto

2014

Applied Physics Letters

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“…The phase-controlled density of states (DOS) of the proximized nanowire makes the SQUIPT an ideal building block for the realization of heat nanovalves [4] or very sensitive and ultra-low-power dissipation magnetometers [5][6][7][8] able to succeed the state-of-the-art SQUID technologies, with particular interest in single-spin detection [9].…”

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Coherent transport properties of a three-terminal hybrid superconducting interferometer

et al. 2017

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Coherent transport properties of a three-terminal hybrid superconducting interferometerVischi, F.; Carrega, M.; Strambini, E.; D'Ambrosio, S.; Bergeret, F. S.; Nazarov, Yuli; Giazotto, F. Important noteTo cite this publication, please use the final published version (if applicable). Please check the document version above. CopyrightOther than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons. Takedown policyPlease contact us and provide details if you believe this document breaches copyrights. We will remove access to the work immediately and investigate your claim. We present an exhaustive theoretical analysis of a double-loop Josephson proximity interferometer, such as the one recently realized by Strambini et al. for control of the Andreev spectrum via an external magnetic field. This system, called ω-SQUIPT, consists of a T-shaped diffusive normal metal (N ) attached to three superconductors (S) forming a double-loop configuration. By using the quasiclassical Green-function formalism, we calculate the local normalized density of states, the Josephson currents through the device, and the dependence of the former on the length of the junction arms, the applied magnetic field, and the S/N interface transparencies. We show that by tuning the fluxes through the double loop, the system undergoes transitions from a gapped to a gapless state. We also evaluate the Josephson currents flowing in the different arms as a function of magnetic fluxes, and we explore the quasiparticle transport by considering a metallic probe tunnel-coupled to the Josephson junction and calculating its I -V characteristics. Finally, we study the performances of the ω-SQUIPT and its potential applications by investigating its electrical and magnetometric properties.

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“…Therefore, the probability for electrons to tunnel between N and S R depends on the sign of the spin. The device resembles the superconducting quantum interference proximity transistor (SQUIPT) [8][9][10][11][12] which has been well-studied in several experiments; the crucial structural difference in our device is that the thermoelectric transistor lies in the presence of the FI layer.…”

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“…22,24 Its advantage is the higher critical temperature of NbN of 15 K. As for the normal metal bridge, it is important to achieve good electric contact with the S R loop in order to develop a sizeable and tunable proximity gap. If, for instance, one uses Al as superconductor for the ring, suitable candidates for the N wire are copper (Cu) 8,9,11,12 or silver (Ag) 29 .…”

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Proposal for a phase-coherent thermoelectric transistor

Giazotto

Robinson

Moodera

et al. 2014

Applied Physics Letters

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Identifying materials and devices which offer efficient thermoelectric effects at low temperature is a major obstacle for the development of thermal management strategies for low-temperature electronic systems. Superconductors cannot offer a solution since their near perfect electron-hole symmetry leads to a negligible thermoelectric response; however, here we demonstrate theoretically a superconducting thermoelectric transistor which offers unparalleled figures of merit of up to ∼ 45 and Seebeck coefficients as large as a few mV/K at sub-Kelvin temperatures. The device is also phasetunable meaning its thermoelectric response for power generation can be precisely controlled with a small magnetic field. Our concept is based on a superconductor-normal metal-superconductor interferometer in which the normal metal weak-link is tunnel coupled to a ferromagnetic insulator and a Zeeman split superconductor . Upon application of an external magnetic flux, the interferometer enables phase-coherent manipulation of thermoelectric properties whilst offering efficiencies which approach the Carnot limit.It is known that electron-hole symmetry breaking is essential for a material to posses a finite thermoelectric figure of merit 1,2 . In principle, conventional superconductors have a near perfect symmetric spectrum and therefore are not suitable for thermoelectric devices. However, if the density of states is spin-split by a Zeeman field a superconductor-ferromagnet hybrid device can provide a thermoelectric effect 3-5 with a figure of merit close to 1. Here we propose a multifunctional phase-coherent superconducting transistor in which the thermoelectric efficiency is tunable through an externally applied magnetic flux. A giant Seebeck coefficient of several mV/K and a figure of merit close to ∼ 45 is predicted for realistic materials parameters and materials combinations.The phase-coherent thermoelectric transistor is based on two building blocks. The first one is sketched in Fig. 1(a) and consists of a superconducting film (S R ) tunnel-coupled to a normal metal (N) by a ferromagnetic insulator (FI). The latter induces an exchange field (h) in S R which leads to a Zeeman spin-split superconducting DoS. The spectrum for spin-up (↑) and spin-down (↓) electrons is given bywhere| is the conventional Bardeen-Cooper-Schrieffer DoS in a superconductor, E is the energy, ∆ R is the order parameter, and Γ accounts for broadening. Due to the presence of the spin-splitting field, ∆ R depends on temperature (T ) and h. While the total DoS of S R , ν S R (E) = ν S R↑ (E) + ν S R↓ (E), is electron-hole symmetric [ Fig. 1(b)], the spin-dependent a) Electronic mail: giazotto@sns.it b) Electronic mail: jjr33@cam.ac.uk c) Electronic mail: sebastian bergeret@ehu.es ν S R↑(↓) (E) components are no longer even functions of the energy. This means that electron-hole imbalance can, in principle, be achieved using a spin-filter contact with a normal metal. This would yield a finite thermoelectric effect 3,4 in the N/FI/S R heterostructure shown in F...

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Tunnel spectroscopy of a proximity Josephson junction

Cited by 42 publications

References 34 publications

Proximity nanovalve with large phase-tunable thermal conductance

Proximity nanovalve with large phase-tunable thermal conductance

Coherent transport properties of a three-terminal hybrid superconducting interferometer

Proposal for a phase-coherent thermoelectric transistor

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