Plasmon reflections by topological electronic boundaries in bilayer graphene

TL;DR

This paper demonstrates that topological chiral modes confined to domain walls in bilayer graphene cause plasmon reflection, with experimental and theoretical analysis revealing distinct interference patterns related to different wall types.

Contribution

It provides a detailed understanding of how topological electronic boundaries influence plasmonic behavior in bilayer graphene, supported by both experimental imaging and theoretical calculations.

Findings

Domain walls host topological chiral modes affecting plasmon reflection.

Two types of plasmonic interference patterns correspond to shear and tensile walls.

Theoretical models match experimental plasmonic profiles quantitatively.

Abstract

Domain walls separating regions of AB and BA interlayer stacking in bilayer graphene have attracted attention as novel examples of structural solitons, topological electronic boundaries, and nanoscale plasmonic scatterers. We show that strong coupling of domain walls to surface plasmons observed in infrared nanoimaging experiments is due to topological chiral modes confined to the walls. The optical transitions among these chiral modes and the band continua enhance the local ac conductivity, which leads to plasmon reflection by the domain walls. The imaging reveals two kinds of plasmonic standing-wave interference patterns, which we attribute to shear and tensile domain walls. We compute the electronic structure of both wall varieties and show that the tensile wall contain additional confined bands which produce a structure-specific contrast of the local conductivity. The calculated plasmonic interference profiles are in quantitative agreement with our experiments.