Department of Chemistry, Columbia University, New York, New York 10027, United States.
Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States.
Nano Lett. 2020 Apr 8;20(4):2843-2848. doi: 10.1021/acs.nanolett.0c00605. Epub 2020 Mar 16.
Electron transport across a molecular junction is characterized by an energy-dependent transmission function. The transmission function accounts for electrons tunneling through multiple molecular orbitals (MOs) with different phases, which gives rise to quantum interference (QI) effects. Because the transmission function comprises both interfering and noninterfering effects, individual interferences between MOs cannot be deduced from the transmission function directly. Herein, we demonstrate how the transmission function can be deconstructed into its constituent interfering and noninterfering contributions for any model molecular junction. These contributions are arranged in a matrix and displayed pictorially as a QI map, which allows one to easily identify individual QI effects. Importantly, we show that exponential conductance decay with increasing oligomer length is primarily due to an increase in destructive QI. With an ability to "see" QI effects using the QI map, we find that QI is vital to all molecular-scale electron transport.
电子在分子结中的输运特性由能量相关的传输函数来表征。传输函数描述了具有不同相位的多个分子轨道（MO）中电子隧穿的情况，这导致了量子干涉（QI）效应。由于传输函数包含干涉和非干涉效应，因此不能直接从传输函数中推断出单个 MO 之间的相互作用。本文中，我们展示了如何将传输函数分解为任意模型分子结的组成干涉和非干涉贡献。这些贡献以矩阵的形式排列，并以 QI 图的形式直观地表示，这使得人们可以轻松识别单个 QI 效应。重要的是，我们表明，随着寡聚物长度的增加，电导呈指数衰减主要是由于破坏性 QI 的增加。通过使用 QI 图来“看到”QI 效应，我们发现 QI 对所有分子尺度的电子输运都至关重要。
