Tobias Wolf, UT-Austin

"Topology, flat bands and interactions in graphene-based van der Waals materials"

Abstract: Van der Waals heterostructures provide a rich platform for emergent physics due to their tunable hybridization of electronic orbital- and spin-degrees of freedom. In particular in twisted-layer structures, the resulting geometric moiré superlattice induces long-wavelength modulations that rearrange the electronic spectrum into minibands. Paradigmatic realizations are graphene on hexa-boron nitride (g/hBN) and twisted bilayer graphene (TBG), now famous for its magic-angle flat bands with strong correlations. I will present (i) my classification for the minibands and their (valley) topology of g/hBN-like continuum models, (ii) an electrically-tunable magnetic instability in TBG away from the magic angle treated with an atomistic tight-binding model with self-consistent mean fields, and (iii) a valley instability in magnetically encapsulated TBG using atomistic and effective moiré tight-binding models with mean fields. The presented results exemplify how Van der Waals materials provide a powerful playground to control the electronic properties by means of moiré engineering, and demonstrate different methods to treat the superstructure and correlations therein.