Flat bands in hetero-biaxially strained bilayer graphene without relaxation

Determine whether biaxial heterostrain without atomic relaxation in bilayer graphene can produce low-energy flat bands comparable to those in twisted bilayer graphene moiré patterns, or establish their absence under realistic tight-binding parameters.

Background

The authors note that moiré patterns do not automatically yield flat bands; specifically, in their tight-binding calculations they were unable to obtain flat bands from hetero-biaxial strain without relaxation, contrasting with twisted bilayers where flat bands emerge near magic angles.

Clarifying whether such strain-only configurations can host flat bands—or why they cannot—would refine the design space for engineering flat-band physics without rotational misalignment.