Light-induced States and Phase Transitions in Quantum Materials investigated by Photoemission Spectroscopy and Epitaxial Synthesis

Abstract

In condensed matter physics, a field of the study on phases of matter and their transitions, light-induced states and phase transitions have attracted significant attention due to their importance in both fundamental research and applications. This thesis will specifically delve into three compelling studies: (1) Floquet-Bloch states, photon-dressed Bloch states, were investigated in graphene. These states are generated by a time-periodic potential of light, closely related to the topic of Floquet engineering. (2) A light-induced insulator-to-metal transition was observed in Sr₂IrO₄, providing valuable insights into the fundamental characteristics of its ground states. (3) A light-induced topological phase transition (from a Z₂ topological insulator to a trivial insulator) was investigated in Bi-doped (Pb,Sn)Se thin-films. For these studies, we employed time- and angle-resolved photoemission spectroscopy (trARPES) and molecular beam epitaxy (MBE). Through in-depth investigation into these phenomena, this thesis seeks to contribute to the broader understanding of light-matter interactions in quantum materials.