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Title: Supersonic light-driven domain walls in a quantum material
Abstract: Quantum materials exhibit fascinating phenomena when perturbed on short time scales or viewed at small length scales. For example, ultrafast light pulses can induce nonequilibrium behaviors that are thermally inaccessible. In addition, rich mesoscopic heterogeneity often exists in equilibrium, including the presence of domain walls that lie at the interface between different domains. Merging direct spatial imaging with ultrafast time resolution therefore has tremendous potential to reveal intriguing lightinduced domain wall dynamics but is experimentally challenging. In this talk, I will show how ultrafast optical pulses can be harnessed to both image and dynamically manipulate the antiferromagnetic domain walls in a Mott insulator. I will first introduce the technique of optical second-harmonic generation as a powerful local probe of the antiferromagnetic order parameter, which enables direct visualization of antiferromagnetic domains and domain walls. I will then highlight our discovery of light-driven antiferromagnetic domain walls that move with record-high supersonic speeds. Systematic experimental investigations point towards a non-trivial driving mechanism related to photon helicity and domain wall chirality. These results provide an unprecedented view of domain wall dynamics in quantum materials. Finally, I will discuss emerging research opportunities to design quantum materials at the nanoscale to unlock new nonequilibrium phenomena.
Brief bio: Dr. Seyler received his PhD in Physics from the University of Washington in 2018 where he studied the optical properties of two-dimensional materials and their heterostructures under Professor Xiaodong Xu. Currently he is a postdoctoral scholar at tthe California Institute of Technology under Professor David Hsieh where he is exploring nonlinear and ultrafast optical phenomena in strongly correlated quantum materials.