演講題目: Electronic structure studies of low-Tc and high-Tc superconductors
摘 要: In this talk, the technique of angle-integrated and angle-resolved photoemission spectroscopy will be introduced as an experimental tool to study the electronic structure of materials. After a brief discussion on applications of ultra-violet and x-ray photoemission spectroscopy to study metal-insulator transitions and semiconductors, we use the technique to study the evolution of electronic structure of a variety of superconductors across their transition temperature (Tc). Examples including low-Tc elemental metals and oxides, transition metal dichalcogenides, high-Tc copper oxides and Fe-based superconductors will be discussed. While some low-Tc superconductors can be explained by the simple Bardeen Cooper Schrieffer (BCS) model based on an isotropic electron-phonon coupling, the high-Tc copper oxides indicate the role of strong electron-electron correlations in superconductivity. The experimental results allow us to characterize weak-coupling to strong-coupling s-wave superconductivity, dx2−y2 superconductivity, as well as the more exotic dx2−y2+is and an octet node type superconductivity.
