Basic concepts of "quantum interference effects" in simple-scatterer and "single-molecule junctions"

Abstract

Using the "tight binding model", we studied "single electron transport properties" of a one-dimensional chain for many physical models by using a numerical decimation method and implementing Quantum Transport FORTRAN Code (QTFC). The constructive and destructive quantum interference were presented and the calculations show that at a dangling atom, "the transmission coefficient as a function of energy T(E)" is destroyed to the zero due to anti-resonance phenomenon that expresses how the transmission coefficient shifting when we vary E2 value. In the other hand, we produced the typical Fano line shape as example for a single molecule junction with a "side group" produces a "Fano resonance" when the energy, E, of the "incident electron" is close to "an energy level" in the side group. The transmission coefficient as a function of energy was found by deriving the "transfer matrix" that enables us to find the energy of a "bound state" and to calculate "the transmission of an electron" through a system of single-double dangling atom. Using "density functional theory", we investigated the "electron transport" through a "single molecule". The DFT is combined with a "Green's function scattering approach". The calculation of "transmission coefficient as a function of energy" for "single molecule benzene ring" attached to two nanogap gold. The para and meta positions junction were studied and the calculations show that higher conductance in the para position compared to the meta position. We investigated the electron transport through single-molecule benzene, in one hand with pyridyle group. On the other hand, with thiol group. The calcultion shows that at "pyridyle group", we have LUMO dominant transport when the LUMO level closes to EFDFT=O eV. Whereas, with thiol group we have HOMO dominant transport when the HOMO level closes to EFDFT=O eV. This study establishes that quantum interference in the "single-molecule" and construct a "quantitative view" of "transport mechanisms" through nanoscale electronics devices.