Spectroscopic studies of the electronic structures of superconductors and topological materials
This dissertation presents experimental research on the electronic structures of threecrystalline materials using a combination of spectroscopic techniques. In the topological material Hf2Te2P, topological surface states are revealed using scanning tunneling microscopy and angle-resolved photoemission spectroscopy. The surface states exist in distinct regions of energy-momentum space and show the potential for the conductive properties of the material to be controlled via tuning of the Fermi level. In the cuprate superconductor La1.475Nd0.4Sr0.125CuO4, the effects of uniaxial stress on the strong electronic correlations are measured using resonant x-ray scattering. Uniaxial stress is shown to be a powerful tool for tuning the electronic phases of the material by causing large decreases in the onset temperatures of both the charge stripes and structural deformations. In the iron-based superconductor FeSe0.77S0.23, charge ordering is identified using scanning tunneling spectroscopy. The presence of charge order originating from orbital-selective electronic correlations provides new insight into development of superconductivity in the FeSe1−xSx family. Altogether, these studies uncover new electronic properties of the materials with the goal of finding practical uses of their unique properties.