Two-dimensional material like graphene and Transition Metal Dichalcogenide (TMDC) has attracted extensive research interest due to their unique electronic and optical properties. Among those, valley specific optical section rule and strong many body interactions are two important ingredients. In this talk, I will first introduce our recent work on ultrafast manipulation of valley pseudo spin using optical Stark effect. Our work completes the ‘generation-manipulation-detection’ paradigm for valleytronics. Then, I will demonstrate using ultrafast pump-probe techniques to study exciton-exciton annihilation process in the TMDC, an important many-body phenomenal in the system. Last, I will tell a story of how many body interaction and valley selection rule modify the material’s chiral response under strong laser excitation condition.
De-Zheng Sun is a postdoctoral scholar in the department of applied physics at Stanford University. He received his Ph.D. in Physics at University of California, Riverside (2011), B.S. in applied physics in University of Science and Technology of China (2006). His current research interest is using ultrafast laser pulse to study the optical response of the two-dimensional material.