Hund’s Exchange in Electrochemistry: Electronic Properties of Real-Life Battery Materials from a Dynamical Mean Field Perspective
Silke Biermann, CPHT – Ecole Polytechnique, Institut Polytechnique de Paris
Progress in dynamical mean field-based electronic structure methods over the last years has provided us with precious tools allowing for a microscopic understanding of electronic mechanisms at work in correlated materials, including functional materials. In this talk, we will focus on layered transition metal sulphides studied for battery applications. Analysing the electronic structure, energetics and intercalation voltage, we find that Hund’s exchange coupling plays a crucial role for the electrochemistry of these compounds. We identify the battery charging process as a transition from a high-spin Mott insulator to a low-spin correlated metal. We argue that a deeper understanding of the microscopic mechanisms at work in such materials might contribute to paving the way to better battery materials in the future.
How to read between the lines of electronic spectra: the diagnostics of fluctuations in strongly correlated electron systems
Thomas Schäfer, Max Planck Institute for Solid-State Research, Stuttgart
While calculations and measurements of single-particle spectral properties often offer the most direct route to study correlated electron systems, the underlying physics may remain quite elusive, if information at higher particle levels is not explicitly included. In this seminar I will present an overview of the different approaches, which have been recently developed and applied to identify the dominant two-particle scattering processes controlling the shape of the one-particle spectral functions and, in some cases, of the physical response of the system. In particular, I will discuss the underlying general idea, the common threads and the specific peculiarities of the proposed approaches. While all of them rely on a selective analysis of the Schwinger-Dyson (or the Bethe-Salpeter) equation, the methodological differences originate from the specific two-particle vertex functions to be computed and decomposed. Finally, I will illustrate the potential strength of these methodologies by means of their applications the two-dimensional Hubbard model, and provide an outlook of future perspective and developments of this route for understanding the physics of correlated electrons.
T. Schäfer and A. Toschi, J. Phys.: Condens. Matter 33, 214001 (2021), https://doi.org/10.1088/1361-648X/abeb44; O. Gunnarsson, T. Schäfer, J. LeBlanc, E. Gull, J. Merino, G. Sangiovanni, G. Rohringer, and A. Toschi, Phys. Rev. Lett. 114, 236402 (2015), https://doi.org/10.1103/PhysRevLett.126.056403