# Voltage Tunable Plasmon Propagation in Dual Gated Bilayer Graphene

## TL;DR

This study theoretically explores how energy asymmetry in dual-gated bilayer graphene influences terahertz plasmon propagation, revealing tunable propagation length and confinement, with implications for reconfigurable plasmonic devices.

## Contribution

It provides a theoretical framework for controlling plasmon propagation in bilayer graphene via dual gating and energy asymmetry, highlighting differences between AA and AB stacking.

## Key findings

- Energy asymmetry increases TM plasmon propagation length.
- AA stacking shows larger propagation length increase than AB.
- Dual gating enables independent modulation of plasmon properties.

## 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.