In this recently published work, we describe modulation of tunnelling probabilities in intramolecular circuits comprising one or two parallel conductance pathways. We show the violation of Kirchhoff's law, where the total conductance of the circuit with two pathways in parallel is not the same as the sum of their individual conductance. The strong interaction (coupling) between the two pathways result in a total conductance which can be explained using the quantum superposition model: G = G1+G2+2√(G1×G2), where G1 and G2 are conductance of parallel intramolecular molecular pathways. We use a rigid molecular wire in metal-molecule-metal tunnelling junction with the possibility of incorporating one or two, low (medium or high) conductance pathways. We use this platform to further manipulate the total conductance of the junction by incorporating a pathway with destructive Quantum Interference. This approach works because a traversing electron interacts with the entire quantum-mechanical circuit simultaneously; Kirchhoff's rules do not apply. We confirm this concept by comparing the conductance of the series across large-area junctions comprising self-assembled monolayers (EGaIn-SAM-AuTS junctions) and single-molecule, scanning tunnelling microscopy break-junctions (STM-BJ).

Understanding the role of parallel intramolecular pathways: Modulating quantum interference in molecular tunnelling junctions

ACS Spring Meeting 2021

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