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Our work about on-surface reaction was published on JACS. Congratulations!

  We study negative differential conductance (NDC) effects in polyporphyrin oligomers with nonlinear backbones. Using a low-temperature scanning tunneling microscope, we selectively controlled the charge transport path in single oligomer wires. We observed robust NDC when charge passed through a T-shape junction, bistable NDC when charge passed through a 90° kink and no NDC when charge passed through a 120° kink. 


    Aided by density functional theory with nonequilibrium Green’s functions simulations,  we attributed this backbone-dependent NDC to bias-modulated hybridization of the electrode states with the resonant transport molecular orbital. The simulations uncover a concerted NDC mechanism: (1) the molecular backbone dictates a molecular  orbital that can serve as a resonant charge transport channel; and (2) the coupling strength between this molecular orbital and the electrodes is strongly modulated by the external bias, specifically, weakened at higher bias. We argue this mechanism is generic in molecular systems, which opens a new route of designing molecular NDC devices.

 

This research was supported by Hong Kong RGC (No. 6301415), N_HKUST601/15 and National Natural Science Foundation of China (Nos. 11674092 and 21561162003).

 

Link:   http://pubs.acs.org/doi/10.1021/jacs.7b11016