AQP Seminar: Floquet moiré engineering
Mediated by ultrafast light-matter interactions, precisely tunable laser sources nowadays allow for the tailored engineering of material properties on demand . In my research, I apply the ideas of ultrafast control to the newly thriving field of twistronics  - the twist-angle-controlled moiré potential engineering of stacked 2D van der Waals heterostructures.
Motivated by the measurement of light-induced Hall currents in graphene , I will first discuss the topological properties of intermediate-angle twisted bilayer graphene (TBG). Employing a full moiré-unit-cell tight-binding model, I will present how circularly polarized light can induce a controllable transition to a topologically nontrivial Floquet band structure . By revealing a surprisingly strong light-matter response for smaller twist angles and associated strongly quenched band velocities, I will slightly switch gears to light-matter couplings (LMCs) in flat-band systems for the second half of my talk.
By pointing out fundamental relations between LMCs and quantum geometry in a generic multiband setting, I will show how the nontrivial properties of the electronic wavefunction sustain a finite light-matter response in flat electronic bands despite a diverging effective mass. Finally, I will employ these conceptual findings to discuss the static and dynamic light-matter response for magic-angle TBG .
The presented results provide an essential step towards ultrafast switching protocols and the future integration of moiré materials into optoelectronic devices.
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