Abstract
We investigate transport through molecular wires whose energy levels are affected by environmental fluctuations. We assume that the relevant fluctuations are so slow that they, within a tight-binding description, can be described by disordered, Gaussian distributed onsite energies. For long wires, we find that the corresponding current distribution can be rather broad even for a small energy variance. Moreover, we analyse with a Floquet master equation the interplay of laser excitations and static disorder. Then the disorder leads to spatial asymmetries such that the laser driving can induce a ratchet current.
Highlights
Each onsite energy En(t) + ξn contains a random contribution ξn that subsumes the influence of environmental fluctuations
We assume that these fluctuations are Gaussian distributed and so slow that we can treat them as static disorder
We have investigated the current through a molecular wire with disordered onsite energies
Summary
The system of the driven molecular wire, the leads, and the coupling between the molecule and the leads, as sketched in figure 1, is described by the Hamiltonian. Each onsite energy En(t) + ξn contains a random contribution ξn that subsumes the influence of environmental fluctuations. We assume that these fluctuations are Gaussian distributed and so slow that we can treat them as static disorder. Where the variance σ 2 is assumed to be position-independent This implies that the energy fluctuations are spatially uncorrelated, such that ξnξn = σ 2δnn. Interaction within a capacitor model and the operator N = n cn†cn describes the number of excess electrons residing on the molecule. The operator cL†q (cR†q) creates an electron in the left (right) lead in state |Lq which is orthogonal to all wire states. Since a typical metal screens all electric fields with a frequency below the plasma frequency, we assume that the bulk properties of the leads are not affected by the laser irradiation
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