비등방성 전자구조에 대한 연엑스선 분광연구

Abstract

In this dissertation, an analysis of the electronic structure from the perspective of microscopic electronic states in an anisotropic system was conducted to understand the underlying principles. Detailed descriptions of XAS and ARPES are provided including the principles, measurement techniques, and analysis. Furthermore, this dissertation introduces the multiplet theory and cluster calculation to analyze XAS spectrum. The first subject is a comprehensive analyses of electronic structure in multiferroic Lu0.5Sc0.5FeO3 using XAS, cluster calculations and ab initio calculations. The ferroelectricity of this system can be adequately explained by the d^0 re-hybridization mechanism, and it was revealed that the Lu element contributes more significantly than Sc in energetically favoring the ferroelectric ground state with greater anisotropy. The second subject is ARPES and DFT calculation study of layered noble metal dichalcogenide PdSe2 for understanding of the origin of strong layer dependent properties. Through ARPES measurements, it was confirmed that the Pd 4d_(〖3z〗^2-r^2 ) band exhibits a significantly large bandwidth. Additionally, DFT calculations revealed that the layer-dependent properties of PdSe2 originate from the unique 4d^9 configuration of Pd, which is attributed to the decrease in charge transfer energy caused by Se-Se dimerization. These comprehensive investigations provide valuable insights into the electronic structures and properties of the studied systems, shedding light on their intriguing phenomena and offering a deeper understanding of their underlying mechanisms.