On the relation between steady-state currents and resonance states in molecular junctions

Abstract

The correlation between the current through a molecular junction and the decay rates of specific resonance states of the molecular conductor is analysed for different molecule–electrodes coupling strengths. Three transport regimes are identified for linear conductors. In the weak coupling regime the current is proportional to the sum of resonance widths and increases with increasing coupling. As the coupling strength increases, the current saturates and the transport becomes ‘Ohmic-like’, i.e. increases linearly with the voltage. In the strong coupling regime the current decreases with the coupling strength. This decrease is associated with a bifurcation of the conductor resonances into narrow (long-lived) ones which dominate the transmission and broad ones which are associated with the formation of localized molecular states at the electrodes interfaces. We show that the nature of the transport is determined by a dimensionless parameter which measures the degree of resonance overlap in the system.