Observation of Electron Coherence and Fabry-Perot Standing Waves at a Graphene Edge

Journal article (2017)

Authors

T. Allen Harvard University
Oles Shtanko Massachusetts Institute of Technology
Amir Yacoby Harvard University, Harvard John A. Paulson School of Engineering and Applied Sciences
Ion Cosma Fulga Weizmann Institute of Science, IFW Dresden
Joel I.J. Wang Massachusetts Institute of Technology
Daniyar Nurgaliev Harvard University
Kenji Watanabe National Institute for Materials Science
Takashi Taniguchi National Institute for Materials Science
A.R. Akhmerov QN/Akhmerov Group - AS , Kavli institute of nanoscience Delft
Pablo Jarillo-Herrero Massachusetts Institute of Technology
Leonid S. Levitov Massachusetts Institute of Technology
Research Group
QN/Akhmerov Group (AS) (TU Delft)
Copyright: © 2017 Monica T. Allen, Oles Shtanko, Ion C. Fulga, Joel I.J. Wang, Daniyar Nurgaliev, Kenji Watanabe, Takashi Taniguchi, A.R. Akhmerov, Pablo Jarillo-Herrero, Leonid S. Levitov, Amir Yacoby
DOI
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https://doi.org/10.1021/acs.nanolett.7b03156
Electron optics Ballistic transport Fabry-Perot interference Graphene edge states Josephson interferometry
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Published Date

13-12-2017

Language

English

Reuse Rights

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Faculty

Applied Sciences

Department

QN/Quantum Nanoscience

Research Group

QN/Akhmerov Group

Abstract

Electron surface states in solids are typically confined to the outermost atomic layers and, due to surface disorder, have negligible impact on electronic transport. Here, we demonstrate a very different behavior for surface states in graphene. We probe the wavelike character of these states by Fabry-Perot (FP) interferometry and find that, in contrast to theoretical predictions, these states can propagate ballistically over micron-scale distances. This is achieved by embedding a graphene resonator formed by gate-defined p-n junctions within a graphene superconductor-normal-superconductor structure. By combining superconducting Aharanov-Bohm interferometry with Fourier methods, we visualize spatially resolved current flow and image FP resonances due to p-n-p cavity modes. The coherence of the standing-wave edge states is revealed by observing a new family of FP resonances, which coexist with the bulk resonances. The edge resonances have periodicity distinct from that of the bulk states manifest in a repeated spatial redistribution of current on and off the FP resonances. This behavior is accompanied by a modulation of the multiple Andreev reflection amplitude on-and-off resonance, indicating that electrons propagate ballistically in a fully coherent fashion. These results, which were not anticipated by theory, provide a practical route to developing electron analog of optical FP resonators at the graphene edge.