Topological valley plasmon transport in bilayer graphene metasurfaces for sensing applications

TL;DR

This paper presents a bilayer graphene metasurface with topological valley modes that enable robust, unidirectional plasmonic transport, which can be exploited for sensitive molecular detection in gas sensors.

Contribution

Introduction of a topological bilayer graphene metasurface with broken mirror symmetry for robust, unidirectional plasmonic modes and a novel molecular sensing mechanism based on Fermi energy variation.

Findings

Demonstrated unidirectional topological valley modes in bilayer graphene.

Designed a gas sensor leveraging Fermi energy shifts affecting transmission.

Showed robustness of modes against disorder and potential for integrated sensing devices.

Abstract

Topologically protected plasmonic modes located inside topological bandgaps are attracting increasing attention, chiefly due to their robustness against disorder-induced backscattering. Here, we introduce a bilayer graphene metasurface that possesses plasmonic topological valley interface modes when the mirror symmetry of the metasurface is broken by horizontally shifting the lattice of holes of the top layer of the two freestanding graphene layers in opposite directions. In this configuration, light propagation along the domain-wall interface of the bilayer graphene metasurface shows unidirectional features. Moreover, we have designed a molecular sensor based on the topological properties of this metasurface using the fact that the Fermi energy of graphene varies upon chemical doping. This effect induces strong variation of the transmission of the topological guided modes, which can be employed as the underlying working principle of gas sensing devices. Our work opens up new ways of developing robust integrated plasmonic devices for molecular sensing.