Understanding circular dichroic angle-resolved photoemission from quantum materials

AbstractThe physics of two-dimensional (2D) material has become a rapidly expanding field ofresearch due to their unique electrical, optical, and mechanical properties, as well astheir wide range of potential applications. The electronic band structure of these ma-terials strongly influences their quantum transport properties, which is critical for next-generation quantum devices based on phenomena such as the quantum Hall effect, spinHall effect, and orbital Hall effect. Consequently, a detailed characterization of the bandstructure, particularly focusing on the orbital angular momentum (OAM) and spin angu-lar momentum (SAM), is essential for realizing the practical applications of 2D materials. Circular dichroic angle-resolved photoemission spectroscopy (CD-ARPES) is a widelyused technique for investigating the OAM of bands, as it has been thought to be able toprobe the OAM of the band structure. This thesis provides an in-depth analysis of various contributions to the CD-ARPESspectra, including the photoionization process, experimental geometry, inter-atomic in-terference, and multiple scattering. These factors are explored in the context of twotechnologically relevant 2D materials, graphene and WSe2, both of which exhibit uniqueelectronic and optical properties that are of interest for quantum and electronic applica-tions. In addition, the thesis provides a detailed characterization of the electronic band struc-ture of 2D magnetic materials, specifically Cr2Ge2Te6 and Fe3GeTe2. Recognizing theimportance of magnetic domain structure in determining the overall magnetic properties, this work also presents a thickness-dependent study of the magnetic domain structure inFe3GeTe2, shedding light on how reduced dimensions influence the magnetic behavior atthe nanoscale.