A Josephson quantum electron pump

Giazotto, Francesco; Spathis, Panayotis; Roddaro, Stefano; Biswas, Subhajit; Taddei, F.; Governale, Michele; Sorba, L.

doi:10.1038/nphys2053

Cited by 107 publications

(120 citation statements)

References 30 publications

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“…The enormous advancement in the production and control of nanotubes and nanowires 11,12 opened up the possibility to couple nanosystems, in a very controlled way, to superconductors [13][14][15] taking advantage of their properties such as the spin-orbit (SO) interaction. Quantum phase transitions and anomalous current-phase relations have been studied in hybrid semiconductorsuperconductor devices.…”

Section: -10mentioning

confidence: 99%

Double quantum dot Cooper-pair splitter at finite couplings

et al. 2016

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We consider the sub-gap physics of a hybrid double-quantum dot Cooper-pair splitter with large single-level spacings, in the presence of tunnelling between the dots and finite Coulomb intra-and inter-dot Coulomb repulsion. In the limit of a large superconducting gap, we treat the coupling of the dots to the superconductor exactly. We employ a generalized master-equation method which easily yields currents, noise and cross-correlators. In particular, for finite inter-and intra-dot Coulomb interaction, we investigate how the transport properties are determined by the interplay between local and nonlocal tunneling processes between the superconductor and the dots. We examine the effect of inter-dot tunneling on the particle-hole symmetry of the currents with and without spinorbit interaction. We show that spin-orbit interaction in combination with finite Coulomb energy opens the possibility to control the nonlocal entanglement and its symmetry (singlet/triplet). We demonstrate that the generation of nonlocal entanglement can be achieved even without any direct nonlocal coupling to the superconducting lead.

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Section: -10mentioning

confidence: 99%

Double quantum dot Cooper-pair splitter at finite couplings

et al. 2016

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“…In contrast with the most recent devices based on proximized diffusive InAs nanowires [30][31][32] , a ballistic T-shaped 2DEG InAs mesa is the basis of our weak-link. The latter is connected to a ringshaped niobium (Nb) electrode and to a third superconducting probe, which is used to measure the voltage drop across the device when threading the loop with an external magnetic field.…”

mentioning

confidence: 99%

A ballistic two-dimensional-electron-gas Andreev interferometer

Amado

Fornieri

Biasiol

et al. 2014

Applied Physics Letters

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We report the realization and investigation of a ballistic Andreev interferometer based on an InAs two dimensional electron gas coupled to a superconducting Nb loop. We observe strong magnetic modulations in the voltage drop across the device due to quasiparticle interference within the weak-link. The interferometer exhibits flux noise down to ∼ 80 µΦ 0 / √ Hz, and a robust behavior in temperature with voltage oscillations surviving up to ∼ 7 K. Besides this remarkable performance, the device represents a crucial first step for the realization of a fully-tunable ballistic superconducting magnetometer and embodies a potential advanced platform for the investigation of Majorana bound states, non-local entanglement of Cooper pairs, as well as the manipulation and control of spin triplet correlations.The combination of ballistic two-dimensional-electrongases (2DEGs) and superconductors (S) may represent a key tool for the investigation of Majorana bound states 1-4 , the generation of solid-state entanglers 5,6 as well as spin triplet superconductivity 7,8 . Up to now, most of the related experimental works have been focused on the study of hybrid devices based on diffusive semiconductor nanowires 9,10 , normal metals 5,6 and ferromagnets 7 . Nevertheless, the structure flexibility and the reduced influence of disorder candidate S-2DEG systems as a promising platform to reach the complete understanding of these effects 11,12 . One of the first steps toward this scope is the fabrication of a ballistic S-2DEG interferometer, in which the phase of quasiparticles is controlled by an external magnetic field and the number of conducting channels can be tailored at will thanks to the presence of side gates. The realization of this kind of device must fulfill two essential conditions: (i) a Schottky barrier-free normal regionsuperconductor interface is necessary to couple the superconductor with the weak link leading to a robust proximity effect, and (ii) the geometrical dimensions of the 2DEG-region must lie below the electron elastic mean free path ensuring the ballistic transport of quasiparticles in the normal region. In the last few years, the major efforts have been put on InAs and InAs/AlSb 2DEG-based hybrid structures. These materials exhibit a larger g-factor and spin-orbit coupling in comparison to those existing in In 0.75 Ga 0.25 As semiconductor alloys [13][14][15][16] , being therefore more attractive for the implementation of a topological non-trivial phase 1-3 . Moreover, the interplay between spin-orbit coupling and spin-splitting (due to the application of an external magnetic field) may lead to an advanced manipulation and control of the triplet superconducting correlations 17,18 with potential application in spintronics. While the early generation of magnetic-flux controlled interferometers consisted of a normal metal (N) region connected to ring-shaped superconductors [19][20][21][22][23][24] , the first realization of a 2DEG-based quasiparticle interferometer was reported by Dimoulas et al. 25 , where ...

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“…Moreover, a possible way around the obstacle is to use the ac Josephson effect to induce periodically timedependent Andreev reflection amplitudes in a hybrid normal-superconducting system. 39 Concrete design of a spin Chern pump based upon the Josephson effect will await future work. While the proposed spin pumping scheme may have the advantage of low noises, its practical application in spintronic devices still relies on the discovery of new TIs with bulk band gaps much greater than room temperature, which determine the temperature range where the spin Chern pumping effect can survive.…”

Section: Discussionmentioning

confidence: 99%

Spin Chern pumping from the bulk of two-dimensional topological insulators

et al. 2015

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Topological insulators (TIs) are a new quantum state of matter discovered recently, which are characterized by unconventional bulk topological invariants. Proposals for practical applications of the TIs are mostly based upon their metallic surface or edge states. Here, we report the theoretical discovery of a bulk quantum pumping effect in a two-dimensional TI electrically modulated in adiabatic cycles. In each cycle, an amount of spin proportional to the sample width can be pumped into a nonmagnetic electrode, which is attributed to nonzero spin Chern numbers C±. Moreover, by using a half-metallic electrode, universal quantized charge pumping conductivities −C±e 2 /h can be measured. This discovery paves the way for direct investigation of the robust topological properties of the TIs.

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A Josephson quantum electron pump

Cited by 107 publications

References 30 publications

Double quantum dot Cooper-pair splitter at finite couplings

Double quantum dot Cooper-pair splitter at finite couplings

A ballistic two-dimensional-electron-gas Andreev interferometer

Spin Chern pumping from the bulk of two-dimensional topological insulators

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