Effects of lithium intercalation in twisted bilayer graphene

We investigate the effects of lithium intercalation in twisted bilayers of graphene, using first-principles electronic structure calculations. To model this system we employ commensurate supercells that correspond to twist angles of $7.{34}^{\ensuremath{\circ}}$ and $2.{45}^{\ensuremath{\circ}}$. From the energetics of lithium absorption we demonstrate that for low Li concentration the intercalants cluster in the AA regions with double the density of a uniform distribution. The charge donated by the Li atoms to the graphene layers results in modifications to the band structure that can be qualitatively captured using a continuum model with modified interlayer couplings in a region of parameter space that has yet to be explored either experimentally or theoretically. Thus, the combination of intercalation and twisted layers simultaneously provides the means for spatial control over material properties and an additional knob with which to tune moir\'e physics in twisted bilayers of graphene, with potential applications ranging from energy storage and conversion to quantum information.