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Observation of the quantum valley Hall state in ballistic graphene superlattices.

ABSTRACT: In graphene superlattices, bulk topological currents can lead to long-range charge-neutral flow and nonlocal resistance near Dirac points. A ballistic version of these phenomena has never been explored. We report transport properties of ballistic graphene superlattices. This allows us to study and exploit giant nonlocal resistances with a large valley Hall angle without a magnetic field. In a low-temperature regime, a crossover occurs toward a new state of matter, referred to as a quantum valley Hall state (qVHS), which is an analog of the quantum Hall state without a magnetic field. Furthermore, a nonlocal resistance plateau, implying rigidity of the qVHS, emerges as a function of magnetic field, and this plateau collapses, which is considered a manifestation of valley/pseudospin magnetism.

SUBMITTER: Komatsu K

PROVIDER: S-EPMC5959303 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Observation of the quantum valley Hall state in ballistic graphene superlattices.

Komatsu Katsuyosih K Morita Yoshifumi Y Watanabe Eiichiro E Tsuya Daiju D Watanabe Kenji K Taniguchi Takashi T Moriyama Satoshi S

Science advances 20180518 5

In graphene superlattices, bulk topological currents can lead to long-range charge-neutral flow and nonlocal resistance near Dirac points. A ballistic version of these phenomena has never been explored. We report transport properties of ballistic graphene superlattices. This allows us to study and exploit giant nonlocal resistances with a large valley Hall angle without a magnetic field. In a low-temperature regime, a crossover occurs toward a new state of matter, referred to as a quantum valley ...[more]

PMID: 29795780

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