Ulčakar Lara, Rejec Tomaž, Kokalj Jure, Sangtarash Sara, Sadeghi Hatef, Ramšak Anton, Jefferson John H, Lambert Colin J
Jožef Stefan Institute, Ljubljana, Slovenia.
Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia.
Sci Rep. 2019 Mar 5;9(1):3478. doi: 10.1038/s41598-019-39937-1.
If simple guidelines could be established for understanding how quantum interference (QI) can be exploited to control the flow of electricity through single molecules, then new functional molecules, which exploit room-temperature QI could be rapidly identified and subsequently screened. Recently it was demonstrated that conductance ratios of molecules with aromatic cores, with different connectivities to electrodes, can be predicted using a simple and easy-to-use "magic number theory." In contrast with counting rules and "curly-arrow" descriptions of destructive QI, magic number theory captures the many forms of constructive QI, which can occur in molecular cores. Here we address the question of how conductance ratios are affected by electron-electron interactions. We find that due to cancellations of opposing trends, when Coulomb interactions and screening due to electrodes are switched on, conductance ratios are rather resilient. Consequently, qualitative trends in conductance ratios of molecules with extended pi systems can be predicted using simple 'non-interacting' magic number tables, without the need for large-scale computations. On the other hand, for certain connectivities, deviations from non-interacting conductance ratios can be significant and therefore such connectivities are of interest for probing the interplay between Coulomb interactions, connectivity and QI in single-molecule electron transport.
如果能够建立简单的指导原则，以理解如何利用量子干涉（QI）来控制电流通过单分子的流动，那么利用室温QI的新型功能分子就可以迅速被识别并随后进行筛选。最近有研究表明，对于具有芳香核且与电极连接方式不同的分子，其电导比可以用一种简单易用的“幻数理论”来预测。与破坏性QI的计数规则和“弯箭头”描述不同，幻数理论涵盖了分子核中可能出现的多种建设性QI形式。在此，我们探讨电导比如何受到电子 - 电子相互作用的影响。我们发现，由于相反趋势的抵消，当开启库仑相互作用和电极引起的屏蔽时，电导比相当稳定。因此，使用简单的“非相互作用”幻数表就可以预测具有扩展π体系的分子电导比的定性趋势，而无需进行大规模计算。另一方面，对于某些连接方式，与非相互作用电导比的偏差可能很大，因此这种连接方式对于探究单分子电子输运中库仑相互作用、连接性和QI之间的相互作用具有重要意义。
