TY - JOUR
T1 - Observation of Electron Coherence and Fabry-Perot Standing Waves at a Graphene Edge
AU - Allen, Monica T.
AU - Shtanko, Oles
AU - Fulga, Ion C.
AU - Wang, Joel I.J.
AU - Nurgaliev, Daniyar
AU - Watanabe, Kenji
AU - Taniguchi, Takashi
AU - Akhmerov, Anton R.
AU - Jarillo-Herrero, Pablo
AU - Levitov, Leonid S.
AU - Yacoby, Amir
PY - 2017/12/13
Y1 - 2017/12/13
N2 - 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.
AB - 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.
KW - Ballistic transport
KW - electron optics
KW - Fabry-Perot interference
KW - graphene edge states
KW - Josephson interferometry
UR - http://resolver.tudelft.nl/uuid:3fec5c5f-e069-4435-8f64-0984e0a648c5
UR - http://www.scopus.com/inward/record.url?scp=85038213378&partnerID=8YFLogxK
U2 - 10.1021/acs.nanolett.7b03156
DO - 10.1021/acs.nanolett.7b03156
M3 - Article
AN - SCOPUS:85038213378
SN - 1530-6984
VL - 17
SP - 7380
EP - 7386
JO - Nano Letters: a journal dedicated to nanoscience and nanotechnology
JF - Nano Letters: a journal dedicated to nanoscience and nanotechnology
IS - 12
ER -