Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 50: Graphene and Carbon Nanotubes
HL 50.5: Vortrag
Donnerstag, 25. März 2010, 10:30–10:45, H15
Inter-valley plasmons and local-field effects in graphene — •Sergey Mikhailov1 and Timur Tudorovskiy1,2 — 1Institute of Physics, University of Augsburg, Germany — 2Department of Physics, Philipps-University of Marburg, Germany
We develop a theory of the linear electromagnetic response of graphene to a scalar-potential field taking into account local field effects [1]. The electromagnetic properties of graphene are characterized by an infinite dielectric matrix over reciprocal lattice vectors. The spectrum of collective excitations (plasmons) is then determined by the determinant of this matrix. We have calculated the dielectric matrix and the spectrum of plasma waves in graphene using the tight binding approximation.
In the long-wavelength limit (the plasmon wavevector is small as compared to the inverse lattice constant) our results reproduce those obtained in the Dirac model [2]. For the wavevectors close to the corners of the hexagon-shaped Brillouin zone we have found (arXiv:0910.2163v1) new low-frequency two-dimensional plasmon modes with a linear spectrum. These intra-band inter-valley plasmons are related to the electronic transitions between the two nearest Dirac cones in the electronic Brillouin zone. Their group velocity exceeds the Fermi velocity of graphene electrons and their Landau damping vanishes at zero temperature.
This work was supported by the Deutsche Forschungsgemeinschaft.
[1] S. L. Adler, Phys. Rev. 126, 413 (1962)
[2] B. Wunsch et. al., New J. Phys. 8, 318 (2006); E. H. Hwang and S. Das Sarma, Phys. Rev. B 75, 205418 (2007)