Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 13: Transport: Poster Session

TT 13.5: Poster

Montag, 26. März 2012, 15:00–19:00, Poster B

Resonant scattering in graphene with a gate-defined chaotic quantum dot — •Martin Schneider and Piet W. Brouwer — Dahlem Center for Complex Quantum Systems and Institut für theoretische Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany

We investigate the conductance of an undoped graphene sheet with two metallic contacts and an electrostatically gated island (quantum dot) between the contacts. Our analysis is based on the Matrix Green Function formalism, which was recently adapted to graphene [1]. We find pronounced differences between the case of a stadium-shaped dot (which has chaotic classical dynamics) and a disc-shaped dot (which has integrable classical dynamics) in the limit that the dot size is small in comparison to the distance between the contacts. In particular, for the stadium-shaped dot the two-terminal conductance shows Fano resonances as a function of the gate voltage, which cross-over to Breit-Wigner resonances only in the limit of completely separated resonances, whereas for a disc-shaped dot sharp Breit-Wigner resonances resulting from higher angular momentum remain present throughout. [1] M. Titov, P. M. Ostrovskyi, I. V. Gornyi, A. Schuessler, and A. D. Mirlin, Phys. Rev. Lett. 104, 076802 (2010)