Prof. Keji Lai, The University of Texas at Austin

"Imaging Sound in Topological Metamaterials"

Abstract: Topological acoustics offers numerous opportunities in manipulating elastic waves that can propagate in solids without being backscattered. In this talk, I will demonstrate the realization of gigahertz topological valley Hall effect in nanoelectromechanical membranes. Propagation of elastic waves through phononic crystals is directly visualized by microwave microscopy with unprecedented sensitivity and spatial resolution. The valley Hall edge states, protected by band topology, are vividly seen in both real- and momentum-space. The robust valleypolarized transport is evident from the wave transmission across local disorder and around sharp corners, as well as the power distribution into multiple edge channels. This work can be further extended to exploit topological physics in integrated acousto-electronic systems for classical and quantum information processing in the microwave regime.

Dr. Lai received his B.S. in Electrical Engineering from Tsinghua University in 2001, and Ph.D. in Electrical Engineering from Princeton University in 2006. He was a Postdoctoral fellow in Applied Physics at Stanford University in 2006 – 2012, an Assistant Professor of Physics at UT-Austin from 2012 – 2018, and an Associate Professor of Physics at UT-Austin from 2018 – present.

Honors and awards: 2013 DOE Early Career Award; 2015 IUPAP Young Scientist Prize in the Structure and Dynamics of Condensed Matter; 2016 Presidential Early Career Awards for Scientists and Engineers (PECASE)