Theory and Models

Abstract

Our experimental motivated a number of calculations, which helped to develop an understanding of the measured electronic structure, as well as motivating additional experiments. Density functional theory calculations, their downfolding onto a set of Wannier orbitals, and minimal tight binding models were all used to understand both the bulk electronic structure of non-magnetic delafossites (discussed in Chap. 3), and the surface states found on their transition metal oxide terminated surfaces (Chap. 6). My aim in this chapter is to describe these theoretical approaches at the level I found useful during the research described in the thesis. For instance, I did not perform the density functional theory calculations myself, but had the pleasure of working with Helge Rosner, the output of whose calculations I have used to address the questions inspired by the experiments. On the other hand, I constructed the tight-binding models which are much less material-specific than the density functional theory calculations, but are easier to manipulate and use to gain direct physical insight. I will briefly describe the theory and approximations underlying each of these approaches, as well as their scope and range of applicability. I will outline the way they were used to study delafossites, and point to the sections where the results of such procedures are shown in this thesis.