Vers une description précise des matériaux spin-orbite fortement corrélés: des modèles aux premiers calculs layered-dmft pour ba2iro4, sr2iro4 et ba2rho4. – (Léo Gaspard / LCPQ / Thesis). – 24/10/2024, 14H

Soutenance de thèse

Léo Gaspard, LCPQ, Salle de Conférence FeRMI 3R4

Abstract:
The interest in spin-orbit correlated materials dates back to 1994 when Strontium Ruthenate Sr2RuO4 was shown to exhibit a superconductive behavior. This discovery reignited the interest of the scientific community toward Ruthenates, but also toward Iridates which share a similar crystallographic structure. Moreover, in the valence bands of Iridates, the bandwidth, the Coulomb interaction and the spin-orbit interaction are all within the same order of magnitude, forcing their theoretical studies to consider these three effects on an equal footing. In this thesis, we study the electronic structure of Ba2IrO4, Sr2IrO4 and Ba2RhO4 . We carefully examine the parametrization and of the models that describe their low-energy spectrum and their resolution using Dynamical Mean Field Theory (DMFT).
We first present a downfolding procedure that allows to build physically relevant models for correlated materials and apply it to the aforementioned materials. We then perform the first five-band DMFT calculations on these materials, showing that the effect of the correlation on the eg bands of these systems is simply a Hartree shift. Finally, we devise a new method that we call layered-DMFT (L-DMFT), which allows to split the correlated space of the five-band model in a part that we treat with a high-precision method and a part that is treated at the mean-field level. We show that this new method yields qualitatively and quantitatively the same results as the complete DMFT method, while making the calculations up to a hundred times faster.