Conclusions and Outlook

Abstract

In this thesis I show the results of our angle resolved photoemission measurements on delafossite metals, and the conclusions were able to draw from these experiments. We were initially motivated by the extraordinarily high conductivity of delafossites, and wanted to study their bulk electronic structure. In both PtCoO$_2$ and PdCoO$_2$ we observed fast bands crossing the Fermi level and forming hexagonal Fermi surfaces. However, the two most relevant novel physical insights arose from unexpected observations, as is often the case in science. We identified the Kondo-like coupling of itinerant and Mott-insulating layers as a cause of the signal observed in the antiferromagnetic delafossite metal PdCrO$_2$, and were able to show that this demonstrates that ARPES can be sensitive to spin-spin correlations. Furthermore, I show how the unusually large spin-splitting we observed on the transition-metal terminated surfaces of delafossites arises as a consequence of the structure of the transition metal oxide layers. These conclusions specific to the individual effects are discussed in detail at the ends of relevant chapters. Here I would like to mention a few general insights I have reached during the course of the research presented in the thesis.