Regensburg 2004 – scientific programme
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TT: Tiefe Temperaturen
TT 27: Nanoelektronik III: Molekulare Elektronik
TT 27.1: Invited Talk
Thursday, March 11, 2004, 09:30–10:00, H19
Molecular wires in electromagnetic fields — •Sigmund Kohler1, Jörg Lehmann1, Sébastien Camalet1,2, and Peter Hänggi1 — 1Institut für Physik, Universität Augsburg, 86135 Augsburg — 2Laboratoire de Physique, ENS Lyon, Frankreich
Electromagnetic ac fields can alter significantly the transport properties of mesoscopic systems like molecular wires. Resonant excitations of electrons can e.g. enhance drastically the currents through molecules. The opposite phenomenon also exists: a proper off-resonant driving field reduces the coherent transport across the molecule resulting in a strong current suppression. Moreover, near such current suppressions, we find characteristic minima and maxima of the shot noise [1]. This effect allows to manipulate current fluctuations by external fields. Molecular wires in laser fields may also be used to study the so-called ratchet effect: in asymmetric molecules, an ac field induces a dc current even in the absence of any bias voltage [2].
The external field is modelled by a periodic time-dependence of the Hamiltonian. This requires a generalization of established transport theories like, e.g., the Landauer formula. Such a generalization, which is based on the Floquet theorem, will be presented and the main differences to the static situation will be discussed.
[1] S. Camalet et al., Phys. Rev. Lett. 90, 210602 (2003).
[2] J. Lehmann et al., Phys. Rev. Lett. 88, 228305 (2002).