Detecting topological currents in graphene superlattices

Topological materials may exhibit Hall-like currents flowing transversely to the applied electric field even in the absence of a magnetic field. In graphene superlattices, which have broken inversion symmetry, topological currents originating from graphene's two valleys are predicted to flow in...

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Bibliographic Details
Main Authors: Gorbachev, R. V., Yu, G. L., Kretinin, A. V., Withers, F., Cao, Y., Mishchenko, A., Grigorieva, I. V., Novoselov, Kostya S., Geim, A. K., Song, Justin Chien Wen, Levitov, Leonid
Other Authors: Massachusetts Institute of Technology. Department of Physics
Format: Article
Language:en_US
Published: American Association for the Advancement of Science (AAAS) 2014
Online Access:http://hdl.handle.net/1721.1/89816
https://orcid.org/0000-0002-4268-731X
Description
Summary:Topological materials may exhibit Hall-like currents flowing transversely to the applied electric field even in the absence of a magnetic field. In graphene superlattices, which have broken inversion symmetry, topological currents originating from graphene's two valleys are predicted to flow in opposite directions and combine to produce long-range charge neutral flow. We observe this effect as a nonlocal voltage at zero magnetic field in a narrow energy range near Dirac points at distances as large as several microns away from the nominal current path. Locally, topological currents are comparable in strength to the applied current, indicating large valley-Hall angles. The long-range character of topological currents and their transistor-like control by gate voltage can be exploited for information processing based on the valley degrees of freedom.