Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, 01062 Dresden, Germany.
Phys Chem Chem Phys. 2013 Sep 7;15(33):13951-8. doi: 10.1039/c3cp44578j. Epub 2013 Apr 5.
Quantum interference (QI) effects in molecular devices have drawn increasing attention over the past years due to their unique features observed in the conductance spectrum. For the further development of single molecular devices exploiting QI effects, it is of great theoretical and practical interest to develop simple methods controlling the emergence and the positions of QI effects like anti-resonances or Fano line shapes in conductance spectra. In this work, starting from a well-known generic molecular junction with a side group (T-shaped molecule), we propose a simple graphical method to visualize the conditions for the appearance of quantum interference, Fano resonances or anti-resonances, in the conductance spectrum. By introducing a simple graphical representation (parabolic diagram), we can easily visualize the relation between the electronic parameters and the positions of normal resonant peaks and anti-resonant peaks induced by quantum interference in the conductance spectrum. This parabolic model not only can predict the emergence and energetic position of quantum interference from a few electronic parameters but also can enable one to know the coupling between the side group and the main conduction channel from measurements in the case of orthogonal basis. The results obtained within the parabolic model are validated using density-functional based quantum transport calculations in realistic T-shaped molecular junctions.
量子干涉（QI）效应对分子器件的影响在过去几年中引起了越来越多的关注，因为它们在电导谱中观察到了独特的特征。为了进一步开发利用 QI 效应的单分子器件，开发简单的方法来控制像反共振或 Fano 线形状这样的 QI 效应的出现和位置，这在理论和实践上都具有重要的意义。在这项工作中，我们从一个带有侧基的著名通用分子结（T 形分子）出发，提出了一种简单的图形方法，可以直观地观察电导谱中量子干涉、Fano 共振或反共振出现的条件。通过引入一个简单的图形表示（抛物线图），我们可以很容易地直观地观察电子参数与电导谱中由量子干涉引起的正常共振峰和反共振峰的位置之间的关系。该抛物线模型不仅可以从几个电子参数预测量子干涉的出现和能量位置，而且可以在正交基的情况下，从测量中得知侧基与主要传导通道之间的耦合。利用基于密度泛函的量子输运计算，在真实的 T 形分子结中验证了抛物线模型的结果。
