Observing Quasiparticle Interplay in Topological Quantum Materials: New Analysis Paradigms for Big Data Spectroscopy

摘要

The topological insulator (TI) is a recently discovered fundamental phase of matter, with unique physical properties that set it apart from their conventional solid state counterparts. TIs are insulating in the bulk yet conducting at their surfaces, and their surface states exhibit exotic behaviors like chirality and robustness to local perturbations. As such, topological insulators are a promising candidate for many future applications in fault-tolerant quantum computing and other novel devices.However, digging into details of the topological surface states brings up new questions. How does their robustness withstand higher levels of disorder? How do they respond to different sources of scattering, such as Coulomb interactions? How can we characterize their responses to different classes of perturbation? The thesis work presented here attempts to address these questions via unconventional spectroscopy techniques and development of new data analysis paradigms.First, I will introduce the key components to this thesis, topological insulators and angle-resolved photoemission spectroscopy (ARPES). Second, I will introduce a novel ARPES analysis paradigm and demonstrate its application to TI compound Bi2Se3. This analysis achieves a single-sample analogue of a doping series, as well as the first experimental observation of quantum hybridization between topological surface and bulk states in a TI. Third, I will present the application of similar methods to investigate correlated electron behavior in a topological Kondo insulator SmB6. Results are presented on the interrelationships observed between the bulk bands and surface bands, and the influential effect of Kondo coherence on setting the stage for their behavior.New error analysis methods needed to be developed to enable robust investigations of spectromicroscopic big data and establish the validity of the findings presented in Chapters 2 and 3. A fourth chapter will outline these procedures as well as other novel measurement and analysis methods that were foundational to the work. Finally, I will conclude the dissertation with a summary and some remarks.