Spatial Profile of Topological Edge States in Periodically Driven Twisted Bilayer Graphene

Periodic driving with a circularly polarised laser in the mid-IR range is capable of inducing non-trivial topology in twisted bilayer graphene (TBG). Here, we study the spatial profile of chiral edge states that emerge at the boundary between opposite chiralities of the spatially-modulated driving field. We find that at small twist angles, the induced gap is highly renormalized by interlayer coupling, and the resulting edge states have a large spatial width of order 10-100 nm which is in the experimentally detectable range. We establish an analytical model based on a continuum approximation about the Dirac points, which predicts the properties of the edge states as a function of twist angle, driving amplitude, and 'sharpness' of the edge. Surprisingly, we found that despite the decrease in moiré unit cell size, increasing twist angle (above 1.1°) increases the edge state width. We support our analytical predictions by a numerical study based on the Bistritzer-MacDonald continuum model, accounting for the drive through both an effective Hamiltonian and a full Floquet approach. The large size of the edge states may provide a feasible route towards the direct detection of Floquet edge states using time and

space-resolved spectroscopic probes.