The emergence of controlled, two-dimensional moir\'e materials has uncovered a new platform for investigating topological physics. 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. 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 simultaneously being insulating in the bulk. A Landauer-Buttiker analysis of measurements on multi-terminal samples allows us to quantitatively assess edge state scattering. We interpret these results as signatures of the predicted topological phase at charge neutrality.
@article{arxiv.2101.03621,
title = {Bulk and Edge Properties of Twisted Double-Bilayer Graphene},
author = {Yimeng Wang and Jonah Herzog-Arbeitman and G. William Burg and Jihang Zhu and Kenji Watanabe and Takashi Taniguchi and Allan H. MacDonald and B. Andrei Bernevig and Emanuel Tutuc},
journal= {arXiv preprint arXiv:2101.03621},
year = {2021}
}