CM Seminar - Linear and nonlinear optical responses in chiral topological semimetals

Abstract: The fundamental difference between electrons in a solid and those in high-energy physics is the absence of Poincare symmetry in lattice systems. This gives rise to a much larger number of possible low energy excitations (known as multi-fold fermions) in solid-state physics. Recent theory and experiments show that semimetals with multi-fold degenerate points could exist in nonmagnetic materials with chiral crystal structures. In my talk, I would like to discuss how do we use light to probe these low-energy excitations near the multi-fold degenerate points by linear and nonlinear optical conductivity measurements.

Short Bio: Liang Wu got his B.S. in Physics from Nanjing University in 2010 and Ph.D in Physics at the Johns Hopkins University in 2015. He was a postdoc fellow at the University of California, Berkeley from 2016 to 2018 before joining the department of Physics and Astronomy at the University of Pennsylvania in July 2018. He has been using terahertz spectroscopy and ultrafast optics to study topological insulators, Weyl semimetals and quantum spin liquids. He received the McMillan Award for outstanding contribution in condensed matter physics from the University of Illinois (2019), the Army Research Office Young Investigator Program (YIP) Award (2019), and the Richard L. Greene Dissertation Award in Experimental Condensed Matter Physics by the American Physical Society (2017).