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Nanoscale imaging of equilibrium quantum Hall edge currents and of the magnetic monopole response in graphene

Title
Nanoscale imaging of equilibrium quantum Hall edge currents and of the magnetic monopole response in graphene
Authors
Uri, AviramKim, YoungwookBagani, KousikLewandowski, Cyprian K.Grover, SameerAuerbach, NadavLachman, Ella O.Myasoedov, YuriTaniguchi, TakashiWatanabe, KenjiSmet, JurgenZeldov, Eli
DGIST Authors
Kim, Youngwook
Issue Date
ACCEPT
Citation
Nature Physics
Type
Article
Article Type
Letter
Keywords
Electric chargeGrapheneHall effect devicesIncompressible flowNanomagneticsSQUIDsTopologyBroken time-reversal symmetryCounterpropagatingFundamental attributesMagnetic monopolesNano-scale imagingNonlinear behavioursQuantum Hall systemsTopological chargesQuantum theory
ISSN
1745-2473
Abstract
Although the recently predicted topological magnetoelectric effect1 and the response to an electric charge that mimics an induced mirror magnetic monopole2 are fundamental attributes of topological states of matter with broken time-reversal symmetry, so far they have not been directly observed in experiments. Using a SQUID-on-tip3, acting simultaneously as a tunable scanning electric charge and as an ultrasensitive nanoscale magnetometer, we induce and directly image the microscopic currents generating the magnetic monopole response in a graphene quantum Hall electron system. We find a rich and complex nonlinear behaviour, governed by the coexistence of topological and non-topological equilibrium currents, that is not captured by the monopole models2. Furthermore, by imaging the equilibrium currents of individual quantum Hall edge states, we reveal that the edge states, which are commonly assumed to carry only a chiral downstream current, in fact carry a pair of counterpropagating currents4, in which the topological downstream current in the incompressible region is counterbalanced by a non-topological upstream current flowing in the adjacent compressible region. The intricate patterns of the counterpropagating equilibrium-state orbital currents provide insights into the microscopic origins of the topological and non-topological charge and energy flow in quantum Hall systems. © 2019, The Author(s), under exclusive licence to Springer Nature Limited.
URI
http://hdl.handle.net/20.500.11750/11072
DOI
10.1038/s41567-019-0713-3
Publisher
Nature Publishing Group
Related Researcher
  • Author Kim, Youngwook Nanomaterials and Quantum Device Lab
  • Research Interests Quantum Transport, Mesoscopic Physics
Files:
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Collection:
Department of Emerging Materials ScienceNanomaterials and Quantum Device Lab1. Journal Articles


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