Control over minivalley polarization and interlayer coupling is demonstrated in double bilayer graphene twisted with an angle of 2.37∘. This intermediate angle is small enough for the minibands to form and large enough such that the charge carrier gases in the layers can be tuned independently. Using a dual-gated geometry we identify and control all possible combinations of minivalley polarization via the population of the two bilayers. An applied displacement field opens a band gap in either of the two bilayers, allowing us to even obtain full minivalley polarization. In addition, the wavefunctions of the minivalleys are mixed by tuning through a Lifshitz transition, where the Fermi surface topology changes. The high degree of control makes twisted double bilayer graphene a promising platform for valleytronics devices such as valley valves, filters and logic gates.
@article{arxiv.2002.05267,
title = {Combined minivalley and layer control in twisted double bilayer graphene},
author = {Folkert K. de Vries and Jihang Zhu and Elias Portoles and Giulia Zheng and Michele Masseroni and Annika Kurzmann and Takashi Taniguchi and Kenji Watanabe and Allan H. MacDonald and Klaus Ensslin and Thomas Ihn and Peter Rickhaus},
journal= {arXiv preprint arXiv:2002.05267},
year = {2020}
}