Sub-Poissonian shot noise in molecular wires

We investigate the transport behavior of polyene molecules sandwiched betweentwo metallic contacts using the non-equilibrium Green's function formalism. Wecalculate both current and noise power as a function of applied voltage andshow that they decrease with increasing size of the polyene molecules. We findthat even with symmetric connection to metallic contacts, current verus voltagecurves can be asymmetric for asymmetrically substituted polyenes. Mostimportantly, we demonstrate a cross-over from Poissonian to sub-Poissonianbehavior in the shot noise as a function of applied voltage. The algorithm fornoise power calculation can be used for designing molecules with low noise.Comment: 3 pages, 2 figures, submitted to Applied Physics Letter