Report Title: A Different Perspective on Scattering Experiments: Insights from Dynamical Mean Field Theory

Speaker: Prof. Gheorghe Lucian Pascut

Date and Time: August 30, 2024, 9:00 AM

Location: Online Meeting (Tencent Meeting ID: 358-328-389)

Organizer: School of Physics and Electronic Engineering

Abstract:

Correlated materials, characterized by strong Coulomb interactions between electrons, are known to exhibit interesting physical properties such as metal-to-insulator transitions, ferroelectricity coexisting with long-range magnetic order, orbital and charge ordering, etc., which are utilized for developing functionalities in electronic devices. The theoretical description of functionalities in correlated materials is highly challenging due to the crucial role played by electronic correlations, which are difficult to incorporate into theoretical methods. In this context, many theoretical approaches for the ab-initio description of strong electronic correlations in solids have been developed recently, among which Density Functional Theory (DFT) combined with Embedded Dynamical Mean Field Theory (eDMFT) has shown great success. Theoretical descriptions of the complex interplay between electronic and structural properties near a transition driven by electronic correlations have only recently become feasible thanks to the development of forces for structural relaxations within the DFT+eDMFT method. As a result of these advancements, it is now possible to quantitatively predict fundamental bulk properties (crystal and magnetic structures, spectral functions, resonant X-ray scattering, etc.) of correlated materials. For the first time, the predictive capability of the DFT+eDMFT method was demonstrated by simultaneously considering structural and electronic degrees of freedom at finite temperatures for correlated materials like NdNiO3, Mn2Mo3O8, Fe2Mo3O8, BiMnO3, and LaMnO3. At the same time, its predictive power was used to investigate the correlation phase diagram for LaNiO2 and copper-doped lead apatite, known as LK-99. Besides accurately capturing the temperature dependence of both electronic and structural properties, the DFT+eDMFT method can predict the existence of novel electronic states of matter, characterized by site or orbital selectivity, where insulating, semi-metallic, and metallic orbitals coexist—states that cannot be captured by other ab-initio methods such as DFT or its extensions. Thus, the DFT+eDMFT method is a powerful tool in materials science due to its predictive capabilities. In this talk, I will present a review of literature and theoretical results for some of the aforementioned correlated materials and attempt to convince you that the synergy between experiments and the predictive power of the DFT+eDMFT method at finite temperatures can guide experiments, design new ones, explain and interpret experimental results, allowing us to gain a deeper understanding of correlated materials. Furthermore, using the DFT+eDMFT method, I will introduce an alternative perspective on the concept of "charge disproportionation/order" in materials and argue that it is synonymous with the emergence of unique states of matter characterized by site or orbital selectivity.

Biography of the Speaker:

Gheorghe Lucian Pascut, Associate Professor at the Department of Forestry, Stefan cel Mare University (USV), Suceava, Romania. He obtained his Ph.D. in Physics from the School of Physics, University of Bristol, United Kingdom.

All faculty members and students are welcome to attend!