Center for Atomic-scale Materials Design (CAMD), Department of Physics, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
Phys Chem Chem Phys. 2011 Aug 28;13(32):14311-7. doi: 10.1039/c1cp20924h. Epub 2011 Jun 28.
Quantum interference (QI) in molecular transport junctions can lead to dramatic reductions of the electron transmission at certain energies. In a recent work [Markussen et al., Nano Lett., 2010, 10, 4260] we showed how the presence of such transmission nodes near the Fermi energy can be predicted solely from the structure of a conjugated molecule when the energies of the atomic p(z) orbitals do not vary too much. Here we relax the assumption of equal on-site energies and generalize the graphical scheme to molecules containing different atomic species. We use this diagrammatic scheme together with tight-binding and density functional theory calculations to investigate QI in linear molecular chains and aromatic molecules with different side groups. For the molecular chains we find a linear relation between the position of the transmission nodes and the side group π orbital energy. In contrast, the transmission functions of functionalized aromatic molecules generally display a rather complex nodal structure due to the interplay between molecular topology and the energy of the side group orbital.
量子干涉（QI）在分子输运结中可能导致电子在某些能量下的传输显著减少。在最近的一项工作中[Markussen 等人，Nano Lett.，2010，10，4260]，当原子 p(z)轨道的能量变化不大时，我们表明，当共轭分子的结构存在这种传输节点时，在费米能级附近的传输节点可以仅从共轭分子的结构预测。在这里，我们放宽了同定能的假设，并将图形方案推广到包含不同原子种类的分子中。我们使用这种图论方案与紧束缚和密度泛函理论计算相结合，研究了具有不同侧基的线性分子链和芳香族分子中的 QI。对于分子链，我们发现传输节点的位置与侧基π轨道能量之间存在线性关系。相比之下，由于分子拓扑和侧基轨道能量之间的相互作用，功能化芳香族分子的传输函数通常显示出相当复杂的节点结构。
