Dresden 2014 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 54: Computational Materials Modelling VIII - Functional materials
MM 54.4: Talk
Thursday, April 3, 2014, 12:45–13:00, IFW D
Modeling the screening in atomically thin layers — •Ralf Hambach1, Philipp Wachsmuth1, Gerd Benner2, and Ute Kaiser1 — 1Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany — 2Carl Zeiss Microscopy GmbH, Carl-Zeiss-Str. 22, 74447 Oberkochen, Germany
In this joint experimental and theoretical work, we investigate the electronic screening in free-standing, tilted graphene as prototype 2D material. To this end, the momentum-dependent electron energy-loss function has been measured by angular-resolved electron energy-loss spectroscopy up to 40eV using a transmission electron microscope (SALVE-I [1]). Corresponding ab-initio calculations in the framework of time-dependent density-functional theory have been performed using a plane-wave pseudopotential code [2,3]. We find very good agreement between experimental and theoretical results both for in-plane and for out-of-plane momentum transfers.
Starting from our ab-intio calculations, we assess the importance of out-of-plane excitations in the electronic screening and discuss the validity of a two-dimensional description of graphene which is often applied in model calculations by neglecting the extension in perpendicular direction. Finally, we discuss simple dielectric models to describe the anisotropy of graphene and the observed plasmon dispersion.
[1] Kaiser et al, Ultramicroscopy 111 1246 (2011)
[2] AbInit: Gonze et al, Comp. Mat. Sci. 25 (2002)
[3] Olevano, Reining, Sottile, http://www.dp-code.org (1998)