# Plasmons in dimensionally mismatched Coulomb coupled graphene systems

## TL;DR

This paper investigates how Coulomb coupling affects plasmon modes in graphene systems of different dimensions, revealing new behaviors with potential applications in plasmonics.

## Contribution

It introduces a detailed calculation of plasmon dispersion in coupled 1D and 2D graphene systems, highlighting the splitting and unique features caused by interlayer Coulomb interactions.

## Key findings

- Splitting of plasmon crossing points into two branches.
- Upper plasmon branch ends at finite wavevector q.
- Structure factor shows single or double peak depending on wavelength.

## Abstract

We calculate the plasmon dispersion relation for Coulomb coupled metallic armchair graphene nanoribbons and doped monolayer graphene. The crossing of the plasmon curves, which occurs for uncoupled 1D and 2D systems, is split by the interlayer Coulomb coupling into a lower and an upper plasmon branch. The upper branch exhibits a highly unusual behavior with endpoints at finite $q$. Accordingly, the structure factor shows either a single or a double peak behavior, depending on the plasmon wavelength. The new plasmon structure is relevant to recent experiments, its properties can be controlled by varying the system parameters, and be used in plasmonic applications.