Abstract:  

‘Magic’-angle twisted bilayer graphene (MATBG) has received a lot of interest due to its flat bands with potentially non-trivial topology that lead to intricate correlated phases. However, control over the fabrication and thus system parameters of such devices is limited. Thus there is an ongoing search for other systems with electronic properties similar to the ones of MATBG, but with more control over the design. In this talk, I will discuss our proposal for an alternative way to realize flat bands, similar to those found in MATBG, but in a single graphene layer with adatoms periodically placed on top [1]. I will present theoretical results based on first principle calculations and group-theoretical analysis that reveals topologically fragile flat bands in the system. I will further discuss the bulk-boundary correspondence associated with nontrivial topology of the flat bands. Our main findings are the corner-localized in-gap states, which are a consequence of the filling anomaly resulting from the nontrivial topology of the flat bands. In the end, I will discuss potential ways to realize this system experimentally.