Understanding Quantum Interference in Molecular Devices Based on Molecular Conductance Orbitals

Electron propagation through a molecular device is determined by its quantum electronic structure. We employ molecular conductance orbitals (MCOs) to predict and interpret quantum interference (QI), which contain more information about the electrodes compared with molecular orbitals (MOs) of an isolated molecule. The phases, amplitudes, and alignment of MCOs determine whether they interfere constructively or destructively, which can be seen directly from projection transmissions and QI maps. We apply this intuitive method to butadiene, benzene, and cyclopentadienyl (Cp) anion so that we can elucidate the mechanism of QI among the whole energy range beyond the Fermi level and demonstrate the unique characteristics of MCOs.