Depolarization
of spontaneous polarization of ferroelectric oxides
can result in the formation of two-dimensional electron gas with high
enough density to support visible surface plasmon polaritons (SPPs).
Since the charge carriers accumulated mainly reside within a nanometer
scale on the surface, it is easily affected by an external covering
layer, such as monolayer graphene. In this work, we report the remarkable
charge transfer from a well-known ferroelectric lithium niobate (LiNbO3, LN) to a neighboring monolayer graphene and consequent striking
effects. The optical properties of graphene-covered LN were investigated
by monitoring the very first reflection (VFR), which is more expedient
to realizing visible SPPs’ excitation and resultant energy
coupling, i.e., the VFR increase and greater dynamic range. This picture
was further confirmed by the double-scattering portion from the composite
LN slab and a striking valley in the transmission spectra. This work
reveals the interactions between bilayer two-dimensional electronic
systems, paving a way toward achieving tunable non-metallic plasmonic
devices.