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Theoretical spectroscopy - from basic developments to real-world applications

Authors: M.A.L. Marques

Ref.: seminar at the Max-Planck-Institut für Festkörperforschung, 18/11/2010 (2010)

Abstract: Theoretical Spectroscopy is a discipline that aims at calculating spectroscopic properties of real materials from first-principles. This field has evolved considerably for the past years, with its success coming from a combination of factors, namely solid theoretical advances, efficient software tools, and ever more powerful computers. In this talk, I will give an overview of our recent work in this field. In particular, I will focus on the use of state-of-the-art many-body methods to describe transition metal oxides. As a real world example, I will take the Cu-based oxides that constitute the delafossite family of transparent conductive materials. It turns out that a good description of their electronic properties -- especially the subtle hybridization between the Cu d and the oxygen p states -- can only be achieved by using self-consistent GW techniques. Furthermore, to describe the experimental data, it is vital to include the phonon contribution to the polarization, which reduces the band-gap by almost 20%. In spite of these successes, these methods remain extremely heavy from the computational point of view. Therefore, the last part of the talk will be devoted to a few ideas on how the insight gained from many-body methods can be used to devise new and more efficient approximations to study larger systems.