Berlin 2012 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 22: Graphene: Structure and Theory II
HL 22.2: Talk
Monday, March 26, 2012, 17:30–17:45, EW 201
Universal infrared absorbance of 2D honeycomb crystals — •Lars Matthes1,2, Friedhelm Bechstedt1, Olivia Pulci2, and Paola Gori3 — 1Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany — 2Dipartimento di Fisica, Università di Roma "Tor Vergata", via della Ricerca Scientifica 1, 00133 Rome, Italy — 3CNR-ISM, Via Fosso del Cavaliere 100, 00133 Rome, Italy
Recently it has been demonstrated experimentally that the optical transparency of graphene is only determined by the Sommerfeld finestructure constant α. [1,2] This result is in agreement with the theory of non-interacting isotropic Dirac fermions with pseudospin and using the vector-potential gauge for the electromagnetic field. [1,3]
Using the complex dielectric function for optical interband transitions, we show the universal result that the low-frequency absorbance obtained for graphene also holds for the 2D group IV crystals silicene and germene, although they are not atomically flat. The result is derived by means of ab-initio electronic-structure calculations for two-dimensional crystals with honeycomb geometry without assuming chiral massless Dirac fermions. It does not depend on the group-IV atom, the sheet buckling, the orbital hybridization, and the gauge used to calculate the optical oscillator strength.
[1] R. R. Nair et al., Science 320, 1308 (2008)
[2] F. Maket al., Phys. Rev. Lett. 101, 196405 (2008)
[3] L. Yang et al., Phys. Rev. Lett. 103, 186802 (2009)