Xiaoyang Zhu1
Columbia University1
Interfaces of two dimensional (2D) van der Waals (vdW) crystals, formed from mechanical transfer stacking or chemical vapor deposition, constitute the most versatile material platforms for the exploration of new physical phenomena, particularly emergent quantum phases. Here we apply femtosecond pump-probe spectroscopy/microscopy to develop a time-domain view of quantum phases at 2D vdW interfaces. Using transitional metal dichalcogenide (TMDC) heterobilayers and 2D layered magnetic semiconductors (e.g., CrSBr), we probe the nature of the quantum phases and their coupling to different degrees of freedom. For TMDC moiré interfaces, we show the robustness of correlated electron phases and their coupling to excitons and phonons. In the layers magnetic semiconductors, we discover the coupling between interlayer electronic hybridization to magnetic order and, as a result, the strong coupling of excitons to coherent magnons. These time-domain views reveal not only the nature of the quantum phases, but also prospects of controlling these quantum phases by light.