Dresden 2003 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 20: Postersitzung IV (Mesoskopische Systeme, Supraleitung: Massivmaterialien, Bandleiter, Pinning, Vortexdynamik, Transporteigenschaften, Korngrenzen)

TT 20.11: Poster

Donnerstag, 27. März 2003, 14:30–19:00, P2c, P2d

Laser control of electronic transport through single molecules — •Jörg Lehmann, Sigmund Kohler, and Peter Hänggi — Institut für Physik, Universität Augsburg

The influence of a laser field on the coherent electron transport through a molecule weakly coupled to leads is investigated. Within a master equation approach combined with Floquet theory for the molecular Hamiltonian, we calculate the current flowing through the different molecule-lead contacts.

As a first application of our formalism, we study directed transport in the absence of a mean external bias. For a broken (generalised) parity symmetry of the driven molecule, we observe a non-zero time-averaged current, i.e. the molecule acts as a coherent quantum ratchet. The direction of this current depends sensitively both on the driving parameters and on the length of the molecule [1,2]. Secondly, a current flowing through the molecule because of an externally applied static voltage can be controlled with the laser: For a two-site molecule connected to two leads, we find for certain driving parameters a strong suppression of the current flowing through the molecule, i.e. a molecular current gate. In a three-contact system, the same effect permits the steering of electrical currents with suitably chosen laser fields [3].

[1] J. Lehmann, S. Kohler, P. Hänggi, and A. Nitzan, Phys. Rev. Lett. 88, 228305 (2002).

[2] J. Lehmann, S. Kohler, P. Hänggi, and A. Nitzan, cond-mat/0208404.

[3] J. Lehmann, S. Camalet, S. Kohler, and P. Hänggi, physics/0205060.