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arXiv · 1805.11777

Observation of the quantum valley Hall state in ballistic graphene superlattices

K. Komatsu·Y. Morita·E. Watanabe·D. Tsuya·K. Watanabe·T. Taniguchi·S. Moriyama
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Abstract

In graphene superlattices, bulk topological currents can lead to long-range charge-neutral flow and non-local resistance near Dirac points. A ballistic version of these phenomena has never been explored. Here, we report transport properties of ballistic graphene superlattices. This allows us to study and exploit giant non-local resistances with a large valley Hall angle without a magnetic field. In the 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 non-local resistance plateau, implying rigidity of the qVHS, emerges as a function of magnetic field, and the collapse of this plateau is observed, which is considered as a manifestation of valley/pseudospin magnetism.

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K. Komatsu, Y. Morita, E. Watanabe, D. Tsuya, K. Watanabe, T. Taniguchi, S. Moriyama. 2018-05-30. Observation of the quantum valley Hall state in ballistic graphene superlattices. https://doi.org/10.1126/sciadv.aaq0194

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