Asymmetry in negative differential resistance driven by electron-electron interactions in two-site molecular devices

We demonstrate that Coulomb interactions within the Hartree-Fock approximation can induce a strong asymmetry in the negative differential resistance of a two-site resonant molecular device. This sharp cutoff at high voltage is generic and independent of the detailed single-particle electronic structure of the system. The intersite coupling between distinct molecular subunits controls a transition from staircase to resonant current-voltage characteristics. These studies clarify the relationship between weak screening and strong nonlinearity. (C) 2001 American Institute of Physics.