Molecular electronics in junctions with energy disorder

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. 1 Author to whom any correspondence should be addressed. New Journal of Physics 10 (2008) 065013 1367-2630/08/065013+10$30.00 © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft