期刊
NANO LETTERS
卷 20, 期 8, 页码 6128-6134出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.0c02230
关键词
Single-molecular junctions; negative differential resistance; vibrational model softening; quadratic electron-vibration coupling
类别
资金
- Natural Sciences and Engineering Research Council (NSERC) of Canada Discovery Grant
- Canada Research Chairs Program
We unravel the critical role of vibrational mode softening in single-molecule electronic devices at high bias. Our theoretical analysis is carried out with a minimal model for molecular junctions, with mode softening arising due to quadratic electron-vibration couplings, and by developing a mean-field approach. We discover that the negative sign of the quadratic electron-vibration coupling coefficient can realize, at high voltage, a sharp negative differential resistance (NDR) effect with a large peak-to-valley ratio. Calculated current-voltage characteristics, obtained based on physical parameters for a nitro-substituted oligo(phenylene ethynylene) junction, agree very well with the measurements. Our results establish that vibrational mode softening is a crucial effect at high voltage, underlying NDR, a substantial diode effect, and the breakdown of current-carrying molecular junctions.
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