This thesis focuses on phenomena arising in two dimensional materials and the software, statistical methods, and analysis tools materials scientists can bring to bear in understanding these phenomena. Concerning materials, we discuss on WS2, a transition metal dichalcogenide, as well as moiré superlattices and heterostructures which contain at least one WS2 layer.
Read front-to-back, it tells the story of software tools built to collect and understand photoemission data, which begins by situating the problems facing photoemission and the scientists who use it (Chapter 1) and culminates in two large, cooperative pieces of software built to furnish solutions: PyARPES (Chapter 2) for the analysis of ARPES data and AutodiDAQt (Chapter 3) which systematizes its collection.
The subsequent experimental chapters demonstrate that scientific insights can readily be drawn with these new tools in hand. Understanding the physics of transition metal dichalcogenides and superlattices constituted from several layers of them (Chapter 4) requires nanoscale photoemission experiments, plenty of exploratory data analysis, and careful treatment of data. We determine that electron localization in WS2/WSe2 is part of a richer moiré phenomenology including inhomogeneous hybridization, miniband formation, and multiple superlattices (Chapter 4). On the way, we include a treatment of the physics of multilayer WS2 where we use ARPES to perform “momentum metrology”. These results lay the groundwork for the interpretation of superlattices, which lay epicycles on top of the multilayer picture. Leaving 2D materials, we explore where novel treatment of data can take photoemission science if hardware innovation stalls (Chapter 5). This section concludes with experiments testing the application of spectral unmixing to contaminated ARPES measurements.
Read back-to-front, the reader infers a different chronology: experimental necessities drove attempts to innovate in the interpretation of photoemission data. The reality is somewhere in between and reflects the author’s preferred aesthetic for the scientific process. First, methodology, interpretation, and the exigencies of scientific results are in constant dialog. Second, shortening the path for feedback between ideas, data, and experiments is the surest path to progress. Chapter 6 contains idle speculations about what might lie down that path.
