Angle resolved photoemission study on multi-layer high temperature superconductor and advances on photoemission spectroscopy
Photoemission spectroscopy (PES) has been established as one of the most important methods to study the electronic structure of molecules, solids and surfaces. It has widespread practical implications in various fields and has significantly contributed to the understanding of fundamental principles in solid state physics.
This thesis introduces two parts of my graduate research work, both related to the PES.
First part of the thesis presents the regular Angle Resolved PES (ARPES) study on a multi-layer high-Tc superconductor Ba2Ca3Cu 4O8F2, which would be predicted as a Mott insulator by conventional wisdom. We find that the electronic structure of this four layer material exhibits clear difference from either conventional hole- or electron-doped cuprate superconductors, making it exceptional to the well known high Tc superconductivity phase diagram. The duplex band structures, the self-doping behavior, the anomalous superconducting gaps and the multiple energy scales associated with its electronic structures not only demonstrate the complexity of this material, but also provide an excellent test example for high Tc superconductivity theories.
The second part of the thesis introduces important recent advances on PES and presents our newly developed Laser based Spin- and Time-Resolved ARPES spectrometer. This new experimental tool not only enables us to perform the spin polarization measurement on photoelectrons, but also provides the capability to perform electronic and spin dynamics measurement by pump-probe experiment scheme. These new capabilities open the door to so many possibilities and will greatly extend the research field of PES. The principle, construction, and commissioning results of the spectrometer are discussed in details, and various experimental proposals are also introduced.