When two van der Waals materials are stacked with a twist angle and/or lattice mismatch, a moiré superstructure arises. Interest in twistronics was ignited by magic-angle graphene bilayers, where band flattening gives rise to strongly correlated phases, including unconventional superconductivity and the quantum anomalous Hall effect. Even more intriguing physics is expected at moiré-modulated surfaces of topological insulators, including chiral Majorana fermions. The moiré potential renormalizes the Dirac dispersion, while magnetism breaks time- reversal symmetry, allowing gaps to open and flat Chern bands to become isolated. In magnetic topological insulator MnBi₂Te₄ moiré engineering may produce high-Chern flat bands, offering a route towards fractional Chern phases, including ones with non-Abelian excitations. While twistronics is extremely productive, it works for limited number of materials and more robust, scalable and reproducible approach is highly desired for moiré creation.

Here, I will present recent experimental results on the moiré-modulated electronic structure of three-dimensional topological insulators covered with two-dimensional magnetic insulators. Lattice mismatch produces moiré patterns with periodicities of 2–10 nm, controlled by film composition and measured by scanning tunnelling microscopy. Using angle-resolved photoelectron spectroscopy, we study Dirac replicas, minigap opening, dispersion renormalization, and possible van Hove singularities. I will also discuss magnetic moiré potentials in initially trivial materials and the prospects for realizing high-Chern flat-band phases without twist.

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https://us06web.zoom.us/j/5081440931

Meeting ID: 508 144 0931

Seminar hosts: Juraj Krsnik i Borna Radatović