Is the Antiresonance in Meta-Contacted Benzene Due to the Destructive Superposition of Waves Traveling Two Different Routes around the Benzene Ring?

2017-04-27T00:00:00Z (GMT) by Daijiro Nozaki Cormac Toher
The well-known antiresonance around the middle of the HOMO–LUMO gap observed in the transmission spectra of the meta-contacted benzene molecular junctions is often explained as being caused by the destructive interference between electronic waves following two different pathways in real space around the phenyl ring. We show one contradictory scenario where this interpretation may break down when one of the bonds in the benzene is attenuated gradually. Interestingly, the dip in the transmission spectra is not attenuated at all even after the complete breaking of the bond. This inconsistency arises from the misinterpretation of the antiresonance observed in energy space as a consequence of the superposition of waves propagating through two independent pathways in real space. We revisit the Landauer model within the Green’s function formalism and propose a different interpretation of the appearance of the antiresonance in energy space in meta-substituted benzene which is compatible with the scenario described above. The quantum interference observed in energy-dependent transmission spectra comes from cancellation between the terms in the Green’s function and is effectively due to interference between the different molecular orbitals.