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.

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