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Detecting topological currents in graphene superlattices

2014; American Association for the Advancement of Science; Volume: 346; Issue: 6208 Linguagem: Inglês

10.1126/science.1254966

1095-9203

Р. В. Горбачев, Justin C. W. Song, Guoliang Yu, Andrey V. Kretinin, Freddie Withers, Yang Cao, Artem Mishchenko, I. V. Grigorieva, Kostya S. Novoselov, Leonid Levitov, A. K. Geim,

Quantum and electron transport phenomena

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 observed this effect as a nonlocal voltage at zero magnetic field in a narrow energy range near Dirac points at distances as large as several micrometers away from the nominal current path. Locally, topological currents are comparable in strength with the applied current, indicating large valley-Hall angles. The long-range character of topological currents and their transistor-like control by means of gate voltage can be exploited for information processing based on valley degrees of freedom.