Dresden 2009 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 26: Transport: Graphene and Carbon Nanotubes
TT 26.16: Talk
Wednesday, March 25, 2009, 18:30–18:45, HSZ 03
Symmetry Classes in Graphene Quantum Dots — •Jürgen Wurm1,2, Adam Rycerz1,3, Inanc Adagideli1, Michael Wimmer1, Klaus Richter1, and Harold Baranger2 — 1Institut für Theoretische Physik, Universität Regensburg, 93040 Regensburg — 2Department of Physics, Duke University, Durham, NC 27708, USA — 3Marian Smoluchowski Institute of Physics, Jagiellonian University, 30059 Krakow, Poland
In view of the recently increased experimental activity in the field of graphene quantum dots [1-2], the need of a theoretical description of these systems is apparent. In this work we study the symmetry classes of open and closed graphene quantum dots through the conductance and energy level statistics [3]. For an abrupt lattice termination, these properties are well described by the standard orthogonal and unitary ensembles of random matrix theory. For a smooth mass confinement, the Hamiltonian and the scattering matrix are block diagonal in the valley degree of freedom. While the effect of this structure is clearly visible in the conductance of open dots, it is suppressed in the spectral statistics of closed dots, because the intervalley scattering time is shorter than the time required required to resolve a level spacing in the closed systems but longer than the escape time of the open systems.
[1] L.A. Ponomarenko et. al., Science 320, 356 (2008)
[2] C. Stampfer, et. al., Appl. Phys. Lett. 92, 012102 (2008)
[3] J. Wurm, Adam Rycerz, Inanc Adagideli, M. Wimmer, K. Richter, H.U. Baranger, arXiv:0808.1008 (2008)