Background: The transport through a quantum-scale device may be uniquely characterized by its transmission eigenvalues n.\nRecently, highly conductive single-molecule junctions (SMJ) with multiple transport channels (i.e., several n > 0) have been\nformed from benzene molecules between Pt electrodes. Transport through these multichannel SMJs is a probe of both the bonding\nproperties at the leadââ?¬â??molecule interface and of the molecular symmetry.\nResults: We use a many-body theory that properly describes the complementary waveââ?¬â??particle nature of the electron to investigate\ntransport in an ensemble of Ptââ?¬â??benzeneââ?¬â??Pt junctions. We utilize an effective-field theory of interacting -electrons to accurately\nmodel the electrostatic influence of the leads, and we develop an ab initio tunneling model to describe the details of the leadââ?¬â??molecule\nbonding over an ensemble of junction geometries. We also develop a simple decomposition of transmission eigenchannels into\nmolecular resonances based on the isolated resonance approximation, which helps to illustrate the workings of our many-body\ntheory, and facilitates unambiguous interpretation of transmission spectra.\nConclusion: We confirm that Ptââ?¬â??benzeneââ?¬â??Pt junctions have two dominant transmission channels, with only a small contribution\nfrom a third channel with n << 1. In addition, we demonstrate that the isolated resonance approximation is extremely accurate and\ndetermine that transport occurs predominantly via the HOMO orbital in Ptââ?¬â??benzeneââ?¬â??Pt junctions. Finally, we show that the transport\noccurs in a leadââ?¬â??molecule coupling regime where the charge carriers are both particle-like and wave-like simultaneously,\nrequiring a many-body description.
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