Quantum-Interference-Controlled Molecular Electronics

Quantum interference in coherent transport through single molecular rings may provide a mechanism to control the current in molecular electronics. We investigate its applicability, using a single-particle Green function method combined with \textit{ab initio} electronic structure calculations. We find that the quantum interference effect (QIE) is strongly dependent on the interaction between molecular $\pi $-states and contact $\sigma $-states. It is masked by $\sigma $ tunneling in small molecular rings with Au leads, such as benzene, due to strong $\pi -\sigma $ hybridization, while it is preserved in large rings, such as [18]annulene, which then could be used to realize quantum interference effect transistors. [Nano Letters 8, 3257 (2008)]