Voltage tunable plasmon propagation in dual gated bilayer graphene

Abstract

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.

Local Optical Conductivity of Bilayer Graphene with Kink Potential

“…It is reported [23,[28][29][30][31] that the surface plasmon reflection at DW solitons can be studied in detail by the near-field infrared nanoscopy for the * Electronic address: heyan ctp@scu.edu.cn reversal stacking configurations in BLG. The DW plasmon also displays a rich phenomenology including tunable subwavelength confinement of light, higher propagation length, plasmon oscillation over a wide range of frequencies as well as supporting the propagation of transverse electric modes [12,32,33]. Meanwhile, optical conductivity measurements can provide a feasible way to probe excitation spectrum of BLG between the gapless states and the continuum bands [34].…”

“…Meanwhile, optical conductivity measurements can provide a feasible way to probe excitation spectrum of BLG between the gapless states and the continuum bands [34]. Up to now, most works focus on the electronic structure and the frequency dependence of the optical conductivity of homogeneous graphene [32,[35][36][37][38]. The local optical conductivity of BLG is strongly sensitive to the atomic-scale stacking order [28] and the band structure which associated with electric-field-induced energy asymmetry [32], leading to the inhomogeneous distributions across DW.…”

“…Up to now, most works focus on the electronic structure and the frequency dependence of the optical conductivity of homogeneous graphene [32,[35][36][37][38]. The local optical conductivity of BLG is strongly sensitive to the atomic-scale stacking order [28] and the band structure which associated with electric-field-induced energy asymmetry [32], leading to the inhomogeneous distributions across DW. To the best of our knowledge, a systematic theoretical study of the optical properties of opposite gated BLG is still lacking.…”