Tunable transport by controlling the structure of a STM molecular junction:synchronizing theory and experiments.

通过在理论和实验中控制和同步分子结的几何结构，我们已经能够最终证明，标准的电子结构方法，如DFT-LDA，不能准确地描述这种系统中的输运。我们现在的目标是在这项工作的基础上，研究哪些方法可以准确地描述运输，并使用我们开发的技术来探索其他系统的特性。在提案的第一阶段，我们成功地开发了系统地改变分子连接点几何形状的程序，允许探索各种不同的运输机制。利用离散傅里叶变换计算了这些结的实际构型，结果与实验数据吻合较好。然而，即使使用正确的几何结构，用DFT-LDA预测的输运行为也与实验中观察到的大不相同。因此，我们可以得出这样的结论：像近藤效应这样的多体现象对于理解这种装置的行为至关重要。在该项目的下一阶段，我们的目标是使用多体微扰理论和自旋解析从头算输运计算等方法来研究和解释导致观察到的分子结行为的机制。这将使我们能够利用第一阶段开发的技术来研究不同的系统，例如，磁性分子结。

Through the control and synchronization of the geometric structure of a molecular junction in both theory and experiment, we have been able to demonstrate conclusively that standard electronic structure methods such as DFT-LDA are incapable of accurately describing transport in such systems. Our goal now is to build on this work, both in terms of investigating which methods do accurately describe transport, and in using the techniques we have developed to explore the properties of other systems. During the first phase of the proposal, we successfully developed procedures to systematically vary the geometry of a molecular junction, allowing a variety of different transport regimes to be probed. The actual configuration of these junctions has been calculated using DFT, and the results corresponded well with the experimental data. However, even using the correct geometry, the transport behaviour predicted using DFT-LDA differs greatly from that observed in experiment. Thus we can conclude that many-body phenomena such as the Kondo effect are crucial for understanding the behaviour of such devices. In the next phase of this project, we aim to use methods such as many-body perturbation theory and spinresolved ab initio transport calculations to investigate and explain the mechanisms responsible for the observed behavior of the molecular junction. This will allow us to exploit the techniques developed in the first phase to investigate different systems such as, e.g., magnetic molecular junctions.