Electrostatic Doping of Moiré Superlattices Controls the Optical Fingerprint of a WSe_2 /Twisted Bilayer Graphene heterostructure

Abstract

We theoretically investigate the optical response of the WSe2 monolayer vertically stacked on twisted bilayer graphene (tBG) under electrostatic doping. In this heterostructure, the doped moiré superlattice of tBG generates a spatially modulated electrostatic potential that couples to the electron and hole constituents of the WSe2 exciton through the screened Coulomb interaction, thereby providing a microscopic mechanism for exciton coupling to the charge-density landscape of the moiré Fermi sea. Focusing on twist angles below the magic angle (1.1°), where electronic correlations are strongly enhanced, we demonstrate that electrostatic doping induces pronounced modifications of the excitonic absorption spectrum, including the emergence of multiple satellite resonances. We show that these spectral features originate from the interplay between the exciton center-of-mass and internal degrees of freedom, together with doping-induced hybridization between Rydberg exciton states of different orbital symmetry. The calculated spectra are in good agreement with previously reported experimental observations and theoretical predictions. Our results establish electrostatic doping in tBG as an effective means of engineering excitonic states in adjacent semiconducting monolayers and provide a pathway toward novel optical sensor devices.