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TT: Fachverband Tiefe Temperaturen

TT 8: TR: Graphene 2 (jointly with MA, HL, and DY)

TT 8.11: Vortrag

Montag, 14. März 2011, 16:45–17:00, HSZ 304

Screening of external electrical fields for different graphene nanoribbons — •Tobias Burnus¹, Gustav Bihlmayer¹, Daniel Wortmann¹, Yuriy Mokrousov¹, Stefan Blügel¹, and Klaus Michael Indlekofer² — ¹Peter Grünberg Institut & Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany — ²Hochschule RheinMain, Unter den Eichen 5, 65195 Wiesbaden, Germany

Graphene nanoribbons (GNR) hold great future promise for field-effect transistor and quantum dot (QD) devices. The gate electrodes and the electric field distribution play a crucial role. In this talk the effect of the screening of an in-plane oriented external electric field due to the electrons in graphene nanoribbons is studied in the framework of density functional theory calculations based on the full potential linearized augmented planewave method. These calculations offer a direct link to the static dielectric constant in the ribbon. We compare armchair ribbons of different width to see the effect of the bandgap on the electric response, as well an orientation with zig-zag edges, which show a metallic edge state. The formation of QDs in structures with both types of edges in an external field is considered. The presence of metallic states, e.g. from a substrate, significantly modifies the behavior of QD states in the external field. The work is supported by the DFG Research Unit 912 “Coherence and Relaxation Properties of Electron Spins”.