Intermolecular Interactions and Quantum Interference Effects in Molecular Junctions

Destructive quantum interference (DQI) leads to a decrease in the conductance of certain well-documented molecules. Experimental observations have revealed both direct and indirect manifestations of DQI, although a comprehensive understanding of the underlying causes of these distinct outcomes remains elusive. In both cases, DQI lowers the conductance, but only the direct case exhibits a characteristic V-shaped dip in differential conductance. Currently, the direct signature has exclusively been observed in monolayers and gated single-molecule systems. In this study, we employ density functional theory to elucidate a plausible explanation for the absence of a direct DQI signature in single molecules. Specifically, we attribute the direct DQI signature to a resonance shift induced by intermolecular interactions, which are absent in the individual molecules. By illustrating the impact of these intermolecular interactions, we emphasize the need for explicit treatment of intermolecular interactions when simulating monolayers.