title: Plasmonic eigenmodes in individual and bow-tie graphene nanotriangles.
abstract: In classical electrodynamics, nanostructured graphene is commonly modeled by the computationally demanding problem of a three-dimensional conducting film of atomic-scale thickness. Here, we propose an efficient alternative two-dimensional electrostatic approach where all calculation procedures are restricted to the graphene sheet. Furthermore, to explore possible quantum effects, we perform tight-binding calculations, adopting a random-phase approximation. We investigate multiple plasmon modes in 20 nm equilateral triangles of graphene, treating the optical response classically as well as quantum mechanically. Compared to the classical plasmonic spectrum which is "blind" to the edge termination, we find that the quantum plasmon frequencies exhibit blueshifts in the case of armchair edge termination of the underlying atomic lattice, while redshifts are found for zigzag edges. Furthermore, we find spectral features in the zigzag case which are associated with electronic edge states not present for armchair termination. Merging pairs of triangles into dimers, plasmon hybridization leads to energy splitting that appears strongest in classical calculations while splitting is lower for armchair edges and even more reduced for zigzag edges. Our various results illustrate a surprising phenomenon: Even 20 nm large graphene structures clearly exhibit quantum plasmonic features due to atomic-scale details in the edge termination.
authors: 1] Center for Nanostructured Graphene (CNG), Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark [2] Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors: Weihua
authors: W
authors: Wang
authors: 1] Center for Nanostructured Graphene (CNG), Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark [2] Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors: Thomas
authors: T
authors: Christensen
authors: 1] Center for Nanostructured Graphene (CNG), Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark [2] Department of Micro and Nanotechnology, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors: Antti-Pekka
authors: AP
authors: Jauho
authors: 1] Center for Nanostructured Graphene (CNG), Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark [2] Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors: Kristian S
authors: KS
authors: Thygesen
authors: 1] Center for Nanostructured Graphene (CNG), Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark [2] Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors: Martijn
authors: M
authors: Wubs
authors: 1] Center for Nanostructured Graphene (CNG), Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark [2] Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors: N Asger
authors: NA
authors: Mortensen