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Using Nonlinear Optics to Shed New Light on Topological Semimetals

Date and Time: Tuesday, February 23, 2021, 01:30pm -
Location: Zoom

Speaker: Rohit P. Prasankumar (Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, NM, USA)

Nonlinear optics has recently emerged as an attractive approach for both probing topological properties and driving topological materials into new states. Here, I will describe our use of ultrafast nonlinear optics to study topological semimetals. I will primarily focus on the Weyl semimetal TaAs, in which we used THz emission spectroscopy was used to provide new insight into the circular photogalvanic effect, ultrafast X-ray diffraction to directly observe coherent longitudinal and shear phonons, and time-resolved second harmonic generation (SHG) to reveal a photoinduced transient symmetry breaking phase. I will also briefly describe our recent SHG measurements on the polar semiconductor BiTeBr as well as high harmonic generation measurements on the chiral topological semimetals CoSi and RhSi. Overall, our studies demonstrate the utility of nonlinear optics in shedding new light on the properties of topological materials.


Dr. Rohit P. Prasankumar received a B.S. in Electrical Engineering from the University of Texas at Austin in 1997 and the M.S. and Ph.D. degrees in Electrical Engineering from MIT in 1999 and 2003, respectively.  His thesis work, completed in 2003, concentrated on developing novel approaches for self-starting mode-locking in solid state lasers.  Dr. Prasankumar subsequently performed his postdoctoral research at Los Alamos National Laboratory (LANL), focusing on ultrafast mid-to-far-infrared dynamics in semiconductor nanostructures and strongly correlated compounds.  He has been a technical staff member at the Center for Integrated Nanotechnologies (CINT) at LANL since 2006, with research interests principally directed towards the measurement of dynamics in complex materials, such as multiferroics, semiconductor nanowires, and topological materials, with high temporal and spatial resolution over a broad spectral range. He is also a research associate professor at the University of New Mexico.

Rohit Prasankumar abstract

Host:  Sang-Wook Cheong

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