Importance of quantum interference in molecular-scale devices

Electron transport is theoretically investigated in a molecular device made of anthracene molecule attached to the electrodes by thiol end groups in two different configurations (para and meta, respectively). Molecular system is described by a simple Huckel-like model (with non-orthogonal basis set of atomic orbitals), while the coupling to the electrodes is treated through the use of Newns-Anderson chemisorption theory (constant density of states within energy bandwidth). Transport characteristics (current-voltage and conductance-voltage) are calculated from the transmission function in the standard Landauer formulation. The essential question of quantum interference is discussed in detail. The results have shown a striking variation of transport properties of the device depending on the character of molecular binding to the electrodes.