  In this paper, we theoretically investigate plasmon propagation
characteristics in AB and AA stacked bilayer graphene (BLG) in the presence of
energy asymmetry due to an electrostatic field oriented perpendicularly to the
plane of the graphene sheet. We first derive the optical conductivity of BLG
using the Kubo formalism incorporating energy asymmetry and finite electron
scattering. All results are obtained for room temperature (300K) operation. By
solving Maxwell's equations in a dual gate device setup, we obtain the
wavevector of propagating plasmon modes in the transverse electric (TE) and
transverse magnetic (TM) directions at terahertz frequencies. The plasmon
wavevector allows us to compare the compression factor, propagation length, and
the mode confinement of TE and TM plasmon modes in bilayer and monolayer
graphene sheets and also study the impact of material parameters on plasmon
characteristics. Our results show that the energy asymmetry can be harnessed to
increase the propagation length of TM plasmons in BLG. AA stacked BLG shows a
larger increase in propagation length than AB stacked BLG; conversely, it is
very insensitive to the Fermi level variations. Additionally, the dual gate
structure allows independent modulation of the energy asymmetry and the Fermi
level in BLG, which is advantageous for reconfiguring plasmon characteristics
post device fabrication.
