A primary goal of modern condensed matter physics is to realize and control novel phases of quantum matter. Although many approaches using material synthesis and static fields have been used at thermal equilibrium, there exists a vast unexplored landscape and associated symmetries at non-equilibrium. Here we can use light to manipulate the space-time symmetries in materials and realize new quantum phenomena that were previously inaccessible. First, we apply terahertz laser pulses to switch the inversion lattice symmetry and induce a topological transition in the Weyl semimetal WTe2. The optically-induced change of lattice structure is crystallographically probed using time-resolved electron diffraction. Second, we apply helical laser pulses to break time-reversal symmetry and tune the energy of specific valleys in monolayer WS2. This approach offers non-equilibrium pathways to control quantum properties of matter on ultrafast timescales.
About the speaker
Edbert Sie is currently a Postdoctoral Geballe Fellow at Stanford University, in the group of Prof. Aaron Lindenberg. He received his PhD in Physics in 2017 at the Massachusetts Institute of Technology (MIT), under the supervision of Prof. Nuh Gedik. His research interests focus on engineering novel phases of quantum materials with light at the atomic length scale and on femtosecond time scale. He is a recipient of the APS Richard L. Green Dissertation Award in Experimental Condensed Matter Physics (2019), Springer Nature Thesis Award (2017), and Stanford GLAM Fellowship (2017).