N. Russo: Electronic Structure of Low-Dimensional and Strongly Correlated Materials Studied with Resonant Inelastic X-ray Scattering

Low dimensional materials and strongly correlated materials offer a range of desirable and tunable properties such as anisotropic conductivity, wide band gaps, or magnetic ordering. In this work, I present the use of soft X-ray resonant inelastic X-ray scattering (RIXS) to investigate a few different material systems which reduced dimensionality, including nanoscale potassium molybdenum oxide (K0.3MoO3), ultra-thin nickel hydroxide and nickel oxide (Ni(OH)2 & NiO), and van der Waals transition metal phosphorous trichalcogenides (MPX3, M= Ni,Fe,Mn, X = S,Se). Using soft X-ray RIXS, I show how reduced dimensionality leads to the disappearance of the charge density wave transition in nanoscale potassium molybdenum oxide. In nickel hydroxide and oxide, I also show that the bandgap of the ultra-thin films is lower than the bulk value consistent with DFT calculations and probe vacancy formation via in situ XPS. Finally, in MPX3 materials, I demonstrate how self-absorption effects influence X-ray absorption spectra and show how partial fluorescence channels can be used to construct a Charge Transfer Multiplet Model for more accurate RIXS spectra predictions.