Dresden 2011 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

O: Fachverband Oberflächenphysik

O 42: Graphene II

O 42.2: Vortrag

Mittwoch, 16. März 2011, 11:30–11:45, WIL B321

Electronic properties of graphene superlattices in a strong magnetic field — •George Pal, Walter Apel, and Ludwig Schweitzer — Physikalisch-Technische Bundesanstalt (PTB), Bundesalee 100, 38116 Braunschweig, Germany

The application of 1-dimensional periodic potentials to graphene leads to new and unexpected phenomena. For example, new Dirac points are induced in the band structure whose positions are controlled by the ratio between the strength and the period of the superlattice potential. Also, the conductivity shows strong resonances when new zero energy states appear.

When graphene superlattices are placed in a magnetic field, the system is described by three length scales: the lattice constant, the period of the superlattice, and the magnetic length. When the parameters of the system are tuned such that these three characteristic lengths are commensurable, then the band structure is modulated in an unique way which has important consequences for the electronic and transport properties.

We study theoretically the electron properties of graphene superlattices in a perpendicular magnetic field within the lattice model. We show that the band structure changes dramatically depending on the ratio between the magnetic length and the superlattice period. Moreover, for certain strengths of the superlattice potential, additional energy gaps open in the Landau bands, which may lead to unusual plateau sequence in the Hall conductivity.