title: Molecular wires acting as coherent quantum ratchets.
abstract: The effect of laser fields on electron transport through a molecular wire weakly coupled to two leads is investigated. The molecular wire acts as a coherent quantum ratchet if the molecule is composed of periodically arranged, asymmetric chemical groups. This setup presents a quantum rectifier with a finite dc response in the absence of a static bias. The nonlinear current is evaluated in closed form within the Floquet basis of the isolated, driven wire. The current response reveals multiple current reversals together with a nonlinear dependence on the amplitude and the frequency of the laser field. The current saturates for long wires at a nonzero value, while it may change sign upon decreasing its length.
authors.affiliation: Institut für Physik, Universität Augsburg, Universitätsstrasse 1, D-86135 Augsburg, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Lehmann
authors.forename: Sigmund
authors.initials: S
authors.lastname: Kohler
authors.forename: Peter
authors.initials: P
authors.lastname: Hänggi
authors.forename: Abraham
authors.initials: A
authors.lastname: Nitzan