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Materials Fall Seminar Series: Giant nonlinear optical responses in polar Weyl semimetals
Start Date: 10/3/2018Start Time: 2:00 PM
End Date: 10/3/2018End Time: 3:00 PM

Event Description
Giant nonlinear optical responses in polar Weyl semimetals

Liang Wu, PhD
Assistant Professor
Department of Physics and Astronomy
University of Pennsylvania 
The second-order optical nonlinearity σ(2)(ω) has been a focus of basic research and technological development for decades as it is both a probe of inversion symmetry breaking in media and the basis for generating coherent light from far-infraredto ultraviolet wavelengths. Here, we focus on the relation between band geometry and nonlinear optics. We measured second harmonic generation (SHG)with incident photon energy from 0.4 eV - 1.6 eV on a polar semimetal TaAs with a sharp resonant peak detected at 0.7 eV, that is larger than previously measured in any crystal. Our discovery of a giant anisotropic σ(2)(ω) in TaAs raises the followingquestions: what is special about TaAs and/or polar metals that accounts for large resonant optical nonlinearity, and, is there a fundamental upper bound on σ(2)(ω) in such inversion breaking crystals? I will describe in the Rice-Mele model based on theband-geometric theory of nonlinear optical response that addresses these questions.
Contact Information:
Name: Dorilona Rose
Phone: x2322
Email: materialsop@drexel.edu
Liang Wu
Attachments For This Event:
    > Seminar Flyer
PISB 104
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