Extraordinary Advances on Photoemission Experiments Zhi-Xun Shen, Professor of Physics, Applied Physics and SSRL, Departments of Physics and Applied Physics Stanford University And Stanford Institute for Materials and Energy Sciences SLAC National Accelerator Laboratory

Photoelectric effect and the Einstein's light quanta interpretation have significantly influenced modern physics and the technologies that follow – ranging from the foundation of quantum mechanics to modern solar cells and photocathodes. Due to its high quantum efficiency, spectroscopy based on the photoelectric effect has become an important tool for modern materials sciences. With much improved resolution and well matched experiments over the last two decades, angle-resolved photoemission spectroscopy (ARPES) has emerged as one of the most important techniques for condensed matter physics. The power of ARPES stems from the direct way it measures the electronic structure by providing the critical energy and momentum relationships of the excitations, and its intimate link to a fundamental microscopic quantity – the single particle Green's function. Photoemission has been at the focal point of debates on some of the deepest questions of quantum physics. In this talk, we will present recent results from novel quantum matter to illustrate the progress. The focus will be the cuprate superconductors, with additional examples from the new Fe pnictide superconductors and topological insulators. If time permits, we will discuss the prospects and strategies to go beyond what is currently possible - ARPES with time resolution (tr-ARPES) and spin resolution (spin-ARPES).