Switching in Molecular Transport Junctions: Polarization Response

We discuss several proposed explanations for the switching and negative differential resistance
(NDR) behavior seen in some molecular junctions. Several theoretical models are discussed, and we present
results of electronic structure calculations on a series of substituted oligo(phenylene ethynylene) molecules.
It is shown that a previously proposed polaron model is successful in predicting NDR behavior, and the
model is elaborated with image charge effects and parameters from electronic structure calculations. This
model now incorporates substituent effects and includes the effects of conformational change, charging,
and image charge stabilization.

我们针对部分分子结(molecular junctions)中观测到的开关效应与负微分电阻(negative differential resistance, NDR)行为，探讨了多种已提出的解释机制。本文同时讨论了多种理论模型，并呈现了针对一系列取代低聚（苯乙炔）(oligo(phenylene ethynylene))分子开展的电子结构计算结果。研究表明，此前提出的极化子模型(polaron model)可有效预测NDR行为；我们通过引入镜像电荷效应(image charge effects)以及电子结构计算得到的参数，对该模型进行了拓展完善。该模型现已纳入取代基效应，同时涵盖了构象变化、电荷效应以及镜像电荷稳定化的相关影响。