Condensed Matter Seminar Series

Title: f-Electron Systems from the GW Perspective: Applications to Lanthanide Oxides

Hong Jiang

Fritz-Haber-Institut, Berlin

Monday Aug. 25,  4:00pm,  Room 298,  Physics Building

Abstract:  Understanding the physics of f-electron systems is regarded as a great challenge in condensed-matter physics today. In many of these materials, the strong localization of the f-electrons gives rise to large many-body interaction effects and in addition leads to severe self-interaction errors in the local-density approximation (LDA). Many-body perturbation theory in the G₀W₀ approximation can describe screening effects among itinerant electrons accurately, and moreover treat exchange exactly. It is therefore a promising approach for investigating these systems. In this work, we first apply the G₀W₀ method to CeO₂ and ThO₂, the ``simplest'' f-electron systems for which the LDA provides a qualitatively correct description, but underestimates band gaps significantly. For both materials, G₀W₀ based on LDA provides an accurate description for the fundamental valence-conduction band gap and the position of f-states. We further apply the  G₀W₀ method to R₂O₃ (R=Ce, Pr, and Nd), in which the f-shell is partially occupied. Since LDA gives qualitatively wrong  metallic ground states for these materials, we apply G₀W₀ corrections on top of LDA+U calculations. We find that (1) The density of  states of Ce₂O₃ is in good agreement with experiment; (2) Band gaps of R₂O₃ for R=La, Ce, Pr and Nd agree quantitatively with optical experimental results; and (3) The trend observed in the relative position of f-bands is in accord with the phenomenological conjecture derived from high-temperature conductivity experiments. Our work shows that the LDA(+U)-G₀W₀ method can treat both itinerant spd bands and localized f-bands accurately for the materials we have considered.