Dresden 2020 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 29: Poster: 2D Materials and their Heterostructures

DS 29.4: Poster

Mittwoch, 18. März 2020, 15:00–18:00, P1A

Tunable spin-orbit coupling in bilayer graphene / WSe2 Heterostructures — •Julia Amann1, Tobias Völkl1, Kenji Watanabe2, Takashi Taniguchi2, Dieter Weiss1, and Jonathan Eroms11Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany — 2NIMS, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan

Heterostructures of graphene and TMDCs are predicted to show strong spin-orbit coupling due to proximity effects. The built-in electric field in bilayer graphene opens an orbital band gap. In addition, applying an external electric field leads to a controllable switching of the spin-orbit splitting.

By van der Waals pickup technique, we fabricated stacks of bilayer graphene and WSe2 on top. We used hBN as an insulator for a Cr/Au topgate. With this dual gated device, it is possible to change the applied transverse electric field and the charge carrier concentration independently. The magnetoconductivity curves show a sharp peak from weak antilocalization as a sign of spin-orbit coupling, which decreases with increasing temperature. Further, we observed a clear dependence of the peak height on the displacement field. This indicates a tunability of the induced spin-orbit coupling.

The peaks were fitted using theory by McCann / Fal'ko, and the resulting spin relaxation times show a giant anisotropy (ratio between the out-of-plane and in-plane time) of ~40. The estimated Rashba- and valley-Zeeman spin-orbit coupling strengths are on the order of 1meV and show a strong dependence on the applied electric field.

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