Regensburg 2022 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 28: Transport in Materials: Diffusion / Electrical Transport & Magnetism
MM 28.3: Vortrag
Donnerstag, 8. September 2022, 10:45–11:00, H44
Non-coplanar magnetism, topological density wave order and emergent symmetry at half-integer filling of moiré Chern bands — •Patrick Wilhelm1, Thomas Lang1, Mathias Scheurer1, and Andreas Läuchli1,2,3 — 1Institut für Theoretische Physik, Universität Innsbruck, 6020 Innsbruck, Austria — 2Laboratory for Theoretical and Computational Physics, Paul Scherrer Institute, 5232 Villigen, Switzerland — 3Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
We study the impact of Coulomb interactions at half-integer filling of the moiré Chern bands of twisted double-bilayer graphene and twisted mono-bilayer graphene, using unbiased exact diagonalization comple-mented by unrestricted Hartree-Fock calculations. For small intra-sublattice tunneling, wAA, a non-coplanar magnetic state is found which has the same symmetries as the tetrahedral antiferromagnet of the triangular moiré lattice and can be thought of as a skyrmion lattice commensurate with the moiré scale. The antiferromagnetic order competes with a set of ferromagnetic, topological charge density waves, which are favored for larger wAA and are associated with an approximate emergent O(3) symmetry, 'rotating' the different charge density wave states into each other. Exhibiting a finite charge gap and Chern number C=|1|, the formation of charge density wave order which is intimately connected to a skyrmion lattice phase is consistent with recent experiments on these systems.