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

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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.