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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 10: Multiferroics and Magnetoelectric Coupling II (joint session MA/KFM)
KFM 10.4: Vortrag
Mittwoch, 18. März 2020, 15:45–16:00, HSZ 401
In-plane magnetoelectric response in bilayer graphene — •Paul Wenk1, Michael Kammermeier2, and Ulrich Zülicke2 — 1Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany — 2School of Chemical and Physical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand
A graphene bilayer shows an unusual magnetoelectric response whose magnitude is controlled by the valley-isospin density, making it possible to link magnetoelectric behavior to valleytronics. Complementary to previous studies, we consider the effect of static homogeneous electric and magnetic fields that are oriented parallel to the bilayer’s plane. Starting from a tight-binding description and using quasidegenerate perturbation theory, the low-energy Hamiltonian is derived, including all relevant magnetoelectric terms whose prefactors are expressed in terms of tight-binding parameters. We confirm the existence of an expected axion-type pseudoscalar term, which turns out to have the same sign and about twice the magnitude of the previously obtained out-of-plane counterpart. Additionally, small anisotropic corrections to the magnetoelectric tensor are found that are fundamentally related to the skew interlayer hopping parameter γ4. We discuss possible ways to identify magnetoelectric effects by distinctive features in the optical conductivity.
[PRB 100, 075421 (2019)]