Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 35: Poster Session I (Metal, semiconductor and oxide substrates: structure and adsorbates; Graphene)

O 35.79: Poster

Dienstag, 12. März 2013, 18:15–21:45, Poster B1

Optical properties of bilayer graphene — •Faris Kadi and Ermin Malić — Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Germany

We present a microscopic study of the optical properties of Bernal-stacked bilayer graphene. In particular, we show the excitonic absorption and conductance for all possible optical transitions. Our theoretical approach is based on the density matrix formalism in combination with tight-binding wave functions [1]. In contrast to the linear band structure of monolayer graphene, bilayered graphene exhibits four parabolic bands near the Dirac point. This results in bilayer-characteristic features in the absorption spectrum. We find that the low energy spectrum exhibits a pronounced peak, which is induced by interlayer transitions around the Dirac point. In the ultraviolet region, the spectrum exhibits two energetically close absorption peaks resulting from interband transitions at the saddle point of the Brillouin zone. We discuss the optical matrix element determining the strength of different optical transitions as well as the Coulomb interaction accounting for energy renormalization and formation of strongly bound electron-hole pairs.

[1] E. Malić, T. Winzer, E. Bobkin, and A. Knorr, Phys. Rev. B 84, 205406, (2011)