Bulk and Edge Properties of Twisted Double-Bilayer Graphene

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Date

2021-10-10

Authors

Wang, Yimeng
Herzog-Arbeitman, Jonah
Burg, G. William
Zhu, Jihang
Watanabe, Kenji
Taniguchi, Takashi
MacDonald, Allan H.
Bernevig, B. Andrei
Tutuc, Emanuel

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Abstract

The emergence of controlled, two-dimensional moir

e´ materials

1–6 has uncovered a

new platform for investigating topological physics

7–9. Twisted double bilayer graphene (TDBG) has been predicted to host a topologically non-trivial gapped phase with Chern number equal to two at charge neutrality, when half the flat bands are filled

8,9. However, it can be difficult to diagnose topological states using a single measurement because it is ideal to probe the bulk and edge properties at the same time. Here, we report a combination of chemical potential measurements, transport measurements, and theoretical calculations that show that twisted double bilayer graphene can host metallic edge transport while si- multaneously being insulating in the bulk. A Landauer-B¨

uttiker analysis of measurements on multi-terminal samples allows us to quantitatively assess edge state scattering. We in- terpret these results as signatures of the predicted topological phase at charge neutrality.

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