Tunnelling spectroscopy of Andreev states in graphene

Van der Waals heterostructures provide a tunable platform for probing the Andreev bound states responsible for proximity-induced superconductivity, helping to establish a connection between Andreev physics at finite energy and the Josephson effect. A normal conductor placed in good contact with a su...

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Vydáno v:Nature physics Ročník 13; číslo 8; s. 756 - 760
Hlavní autoři: Bretheau, Landry, Wang, Joel I-Jan, Pisoni, Riccardo, Watanabe, Kenji, Taniguchi, Takashi, Jarillo-Herrero, Pablo
Médium: Journal Article
Jazyk:angličtina
Vydáno: London Nature Publishing Group UK 01.08.2017
Nature Publishing Group
Nature Publishing Group (NPG)
Témata:
639/766/119/1003
639/766/119/995
639/925/918/1052
639/925/927/1064
Atomic
Carbon
Classical and Continuum Physics
Complex Systems
Condensed Matter Physics
Conductors
Electronic properties
electronic properties and devices
electronic properties and materials
Electronic structure
Energy
Energy measurement
Energy spectra
Fermi surfaces
Graphene
Heterostructures
Josephson effect
letter
MATERIALS SCIENCE
Mathematical and Computational Physics
Molecular
Optical and Plasma Physics
Phase shift
Physics
Proximity
Proximity effect (electricity)
Spectroscopic analysis
Spectroscopy
Spectrum analysis
superconducting devices
superconducting properties and materials
Superconductivity
Superconductor junctions
Superconductors
Theoretical
Topology
ISSN:1745-2473, 1745-2481
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Shrnutí:Van der Waals heterostructures provide a tunable platform for probing the Andreev bound states responsible for proximity-induced superconductivity, helping to establish a connection between Andreev physics at finite energy and the Josephson effect. A normal conductor placed in good contact with a superconductor can inherit its remarkable electronic properties 1 , 2 . This proximity effect microscopically originates from the formation in the conductor of entangled electron–hole states, called Andreev states 3 , 4 , 5 , 6 , 7 , 8 . Spectroscopic studies of Andreev states have been performed in just a handful of systems 9 , 10 , 11 , 12 , 13 . The unique geometry, electronic structure and high mobility of graphene 14 , 15 make it a novel platform for studying Andreev physics in two dimensions. Here we use a full van der Waals heterostructure to perform tunnelling spectroscopy measurements of the proximity effect in superconductor–graphene–superconductor junctions. The measured energy spectra, which depend on the phase difference between the superconductors, reveal the presence of a continuum of Andreev bound states. Moreover, our device heterostructure geometry and materials enable us to measure the Andreev spectrum as a function of the graphene Fermi energy, showing a transition between different mesoscopic regimes. Furthermore, by experimentally introducing a novel concept, the supercurrent spectral density, we determine the supercurrent–phase relation in a tunnelling experiment, thus establishing the connection between Andreev physics at finite energy and the Josephson effect. This work opens up new avenues for probing exotic topological phases of matter in hybrid superconducting Dirac materials 16 , 17 , 18 .
Bibliografie:ObjectType-Article-1
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National Science Foundation (NSF)
SC0001819; DMR-0819762; ECS-0335765; GBMF4541; TMS-094-1-A-001
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Taiwan Merit Scholarship
Gordon and Betty Moore Foundation (United States)
ISSN:1745-2473
1745-2481
DOI:10.1038/nphys4110