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Molecular Wires Acting as Coherent Quantum Ratchets

Jörg Lehmann·Sigmund Kohler·Peter Hänggi·Abraham Nitzan
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Abstract

The effect of laser fields on the electron transport through a molecular wire being 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 (reflecting avoided quasi-energy crossings) on both, 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.

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Jörg Lehmann, Sigmund Kohler, Peter Hänggi, Abraham Nitzan. 2002-01-25. Molecular Wires Acting as Coherent Quantum Ratchets. https://doi.org/10.1103/physrevlett.88.228305

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