Sharp negative differential resistance from vibrational mode softening in molecular junctions
Abstract
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 ab initio parameters for a nitro-substituted oligo(phenylene ethynylene) junction, agree very well with 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.
Cite
@article{arxiv.2005.11365,
title = {Sharp negative differential resistance from vibrational mode softening in molecular junctions},
author = {Junjie Liu and Dvira Segal},
journal= {arXiv preprint arXiv:2005.11365},
year = {2020}
}
Comments
Main text: 6 pages, 3 figures, 1 table; Supplemental material: 9 pages, 8 figures