Wednesday Colloquium: Dr. Hyowon Park, Columbia University
Title: “Dynamical mean field theory comes of age: new methods for the first principles study of structural, electronic and magnetic properties of materials with strong electronic correlations”
Abstract: Materials with strong electronic correlations pose some of the key scientific challenges of modern condensed matter physics and are promising candidates for future energy and electronics applications. Their unusual properties, including magnetism and correlation-driven metal-insulator transitions, require a theoretical description that goes beyond density functional theory (DFT). A very promising approach is to combine DFT with Dynamical Mean Field Theory (DMFT), but until recently only a few kinds of observables could be computed with this theory. In this talk I present results from our state-of-the-art DFT+DMFT methodology, which enables realistic calculations of structural properties and magnetic responses of materials with nontrivial electronic correlations. As examples of the power of the method we solve the long-standing mystery of the coupled structural and metal-insulator transition in the rare earth nickelates, identifying the insulating phase as a site-selective Mott transition and quantitatively determining the structural and electronic phase diagrams of the rare earth nickelates as a function of pressure and rare earth ion. We compute frequency and momentum dependent magnetic response function of the iron-based superconductor BaFe2As2, showing how the combination of materials specifics and electronic correlations gives rise to a novel interplay of localized and itinerant excitation character. Finally, we use the methods to design oxide superlattices involving massively polar Mott insulators that may have application as photovoltaics. Further applications and open questions are discussed.