Hybrid superconductor–quantum dot devices

Franceschi, Sylvio Hermann De; Kouwenhoven, Leo P.; Schönenberger, Christian; Wernsdorfer, Wolfgang

doi:10.1038/nnano.2010.173

Cited by 423 publications

(407 citation statements)

References 79 publications

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“…Complete control over the I c is attributed to the pseudomagnetic field-induced dephasing of the electron-hole phase-coherent Andreev processes in rippled graphene; this provides a unique route for turning off the supercurrent in JJGs, without sacrificing the junction quality in the supercurrent ON state, nor demanding infinite R n like other nanohybrid supercurrent transistors [19][20][21] . Completely tuneable hybrid superconductor graphene devices can be used for developing novel superconducting quantum information devices 23 , such as the Cooper-pair beam splitter 24,43 for quantum entanglement.…”

Section: Discussionmentioning

confidence: 99%

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Complete gate control of supercurrent in graphene p–n junctions

et al. 2013

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In a conventional Josephson junction of graphene, the supercurrent is not turned off even at the charge neutrality point, impeding further development of superconducting quantum information devices based on graphene. Here we fabricate bipolar Josephson junctions of graphene, in which a p-n potential barrier is formed in graphene with two closely spaced superconducting contacts, and realize supercurrent ON/OFF states using electrostatic gating only. The bipolar Josephson junctions of graphene also show fully gate-driven macroscopic quantum tunnelling behaviour of Josephson phase particles in a potential well, where the confinement energy is gate tuneable. We suggest that the supercurrent OFF state is mainly caused by a supercurrent dephasing mechanism due to a random pseudomagnetic field generated by ripples in graphene, in sharp contrast to other nanohybrid Josephson junctions. Our study may pave the way for the development of new gate-tuneable superconducting quantum information devices.

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Section: Discussionmentioning

confidence: 99%

“…The evidence of ripples in our junction was supported by weak antilocalization (WAL) analysis, which showed that the scattering rate by ripples was substantially enhanced near the CNP. Our study provides a key step towards developing superconducting quantum information devices 23,24 based on graphene technology 12 .…”

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confidence: 96%

Complete gate control of supercurrent in graphene p–n junctions

et al. 2013

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“…Nevertheless, experiments suggest the existence of a regime in which quasiparticle transport dominates also in the subgap region. 21 For a quantum dot coupled to a normal and a superconducting lead, a possible explanation for the subgap features observed in Ref. 1 is given, where a carbon nanotube quantum dot is coupled to a normal and a superconducting contact.…”

Section: Introductionmentioning

confidence: 91%

Subgap features due to quasiparticle tunneling in quantum dots coupled to superconducting leads

2013

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We present a microscopic theory of transport through quantum dot setups coupled to superconducting leads. We derive a master equation for the reduced density matrix to lowest order in the tunneling Hamiltonian and focus on quasiparticle tunneling. For high enough temperatures transport occurs in the subgap region due to thermally excited quasiparticles, which can be used to observe excited states of the system at low bias voltages. On the example of a double quantum dot we show how subgap transport spectroscopy can be done. Moreover, we use the single level quantum dot coupled to a normal and a superconducting lead to give a possible explanation for the subgap features observed in the experiments of Dirks, Chen, Birge, and Mason [Appl. Phys. Lett. 95, 192103 (2009)].

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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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Hybrid superconductor–quantum dot devices

Cited by 423 publications

References 79 publications

Complete gate control of supercurrent in graphene p–n junctions

Complete gate control of supercurrent in graphene p–n junctions

Subgap features due to quasiparticle tunneling in quantum dots coupled to superconducting leads

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

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