Strain induced tunable band gap and optical properties of graphene on hexagonal boron nitride

Abstract: In this study, we highlight the potential of strain engineering in graphene/hBN (hexagonal Boron nitride) 2D heterostructures, enabling their use as wide-range light absorbers with significant implications for optoelectronic applications. We systematically investigate the electronic and optical properties of graphene/hBN under the application of strain, considering various stacking geometries within the framework of density-functional theory. The semimetallic graphene layer upon aligning on the insulating hexagonal boron nitride sheet opens a few tens of meV band gap at the Dirac point due to the induced on-site energy differences on the two sublattices of graphene. Here, we demonstrate that by simultaneously tuning the interlayer distance and lattice constant, this band gap can be significantly increased to 1 eV. Interestingly, in both scenarios (small and large band gaps), the material undergoes a transition from a semiconductor to a semimetallic state. Importantly, the tunability of this band gap is strongly influenced by the specific stacking configuration. We further explored the optical properties across a broad spectrum, revealing that the presence of a strain-induced band gap fundamentally alters how light interacts with the system.