Localized plasmons in bilayer graphene nanodisks

TL;DR

This paper investigates localized plasmonic excitations in bilayer graphene nanodisks, revealing unique doping-dependent behaviors and a novel tunable plasmonic mode in AB-stacked configurations, advancing understanding of graphene plasmonics.

Contribution

It introduces a comprehensive analysis of plasmon modes in bilayer graphene nanodisks, highlighting a new mode in AB-stacked structures and the effects of doping and size on plasmon resonance.

Findings

AA-stacked BLG plasmon resonance is doping independent at low doping.

A new plasmonic mode exists in AB-stacked BLG with energy above interlayer hopping energy.

The new mode can be tuned by doping level or structural size.

Abstract

We study localized plasmonic excitations in bilayer graphene (BLG) nanodisks, comparing AA-stacked and AB-stacked BLG and contrasting the results to the case of two monolayers without electronic hybridization. The electrodynamic response of the BLG electron gas is described in terms of a spatially homogeneous surface conductivity, and an efficient alternative two-dimensional electrostatic approach is employed to carry out all the numerical calculations of plasmon resonances. Due to a unique electronic band structures, the resonance frequency of the traditional dipolar plasmonic mode in the AA-stacked BLG nanodisk is roughly doping independent in the low-doping regime, while the mode is highly damped as the Fermi level approaches the interlayer hopping energy $\gamma$ associated with tunneling of electrons between the two layers. In addition to the traditional dipolar mode, we find that the AB-stacked BLG nanodisk also hosts a new plasmonic mode with energy larger than $\gamma$. This mode can be tuned by either the doping level or structural size, and furthermore, this mode can dominate the plasmonic response for realistic structural conditions.