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Quantum finite-size effects in graphene plasmons

Quantum finite-size effects in graphene plasmons
Quantum finite-size effects in graphene plasmons
Graphene plasmons are emerging as an alternative solution to noble metal plasmons, adding the advantages of tunability via electrostatic doping and long lifetimes. These excitations have been so far described using classical electrodynamics, with the carbon layer represented by a local conductivity. However, the question remains, how accurately is such a classical description representing graphene? What is the minimum size for which nonlocal and quantum finite-size effects can be ignored in the plasmons of small graphene structures? Here, we provide a clear answer to these questions by performing first-principles calculations of the optical response of doped nanostructured graphene obtained from a tight-binding model for the electronic structure and the random-phase approximation for the dielectric response. The resulting plasmon energies are in good agreement with classical local electromagnetic theory down to ~10 nm sizes, below which plasmons split into several resonances that emphasize the molecular character of the carbon structures and the quantum nature of their optical excitations. Additionally, finite-size effects produce substantial plasmon broadening compared to homogeneous graphene up to sizes well above 20 nm in nanodisks and 10 nm in nanoribbons. The atomic structure of edge terminations is shown to be critical, with zigzag edges contributing to plasmon broadening significantly more than armchair edges. This study demonstrates the ability of graphene nanostructures to host well-defined plasmons down to sizes below 10 nm, and it delineates a roadmap for understanding their main characteristics, including the role of finite size and nonlocality, thus providing a solid background for the emerging field of graphene nanoplasmonics.
1936-0851
1766-1775
Thongrattanasiri, Sukosin
24d4678f-b0c0-4591-b9ed-9554d6181065
Manjavacas, Alejandro
4be9f6f6-2641-4352-8508-33d99566eacd
García de Abajo, F.Javier
07e3df24-ab3b-4a70-af18-188db066aa1a
Thongrattanasiri, Sukosin
24d4678f-b0c0-4591-b9ed-9554d6181065
Manjavacas, Alejandro
4be9f6f6-2641-4352-8508-33d99566eacd
García de Abajo, F.Javier
07e3df24-ab3b-4a70-af18-188db066aa1a

Thongrattanasiri, Sukosin, Manjavacas, Alejandro and García de Abajo, F.Javier (2012) Quantum finite-size effects in graphene plasmons. ACS Nano, 6 (2), 1766-1775. (doi:10.1021/nn204780e).

Record type: Article

Abstract

Graphene plasmons are emerging as an alternative solution to noble metal plasmons, adding the advantages of tunability via electrostatic doping and long lifetimes. These excitations have been so far described using classical electrodynamics, with the carbon layer represented by a local conductivity. However, the question remains, how accurately is such a classical description representing graphene? What is the minimum size for which nonlocal and quantum finite-size effects can be ignored in the plasmons of small graphene structures? Here, we provide a clear answer to these questions by performing first-principles calculations of the optical response of doped nanostructured graphene obtained from a tight-binding model for the electronic structure and the random-phase approximation for the dielectric response. The resulting plasmon energies are in good agreement with classical local electromagnetic theory down to ~10 nm sizes, below which plasmons split into several resonances that emphasize the molecular character of the carbon structures and the quantum nature of their optical excitations. Additionally, finite-size effects produce substantial plasmon broadening compared to homogeneous graphene up to sizes well above 20 nm in nanodisks and 10 nm in nanoribbons. The atomic structure of edge terminations is shown to be critical, with zigzag edges contributing to plasmon broadening significantly more than armchair edges. This study demonstrates the ability of graphene nanostructures to host well-defined plasmons down to sizes below 10 nm, and it delineates a roadmap for understanding their main characteristics, including the role of finite size and nonlocality, thus providing a solid background for the emerging field of graphene nanoplasmonics.

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More information

Published date: 4 January 2012
Organisations: Optoelectronics Research Centre

Identifiers

Local EPrints ID: 337811
URI: http://eprints.soton.ac.uk/id/eprint/337811
ISSN: 1936-0851
PURE UUID: b56e359d-13a1-4009-b504-e15fafa5e733

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Date deposited: 03 May 2012 14:14
Last modified: 14 Mar 2024 10:58

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Contributors

Author: Sukosin Thongrattanasiri
Author: Alejandro Manjavacas
Author: F.Javier García de Abajo

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