Shedding New Light on Dirac Materials with Nonlinear Optics
11:00 - 12:00
Rohit P. Prasankumar
Los Alamos National Laoratory, Center for Integrated Nanotechnologies, USA
CFEL (Bldg. 99)
Seminar Room IV, O1.111
Nonlinear optics has recently emerged as an attractive approach for both probing topological properties and driving Dirac materials into new states. Here, I will describe our use of ultrafast nonlinear optics to study three representative Dirac materials: graphene micro-ribbons, topological insulators, and Weyl semimetals.
We used terahertz (THz) magneto-optical spectroscopy to examine periodic
arrays of graphene micro-ribbons, enabling us to control the
transmission and Faraday rotation spectra of THz pulses via coupling to
discretized magnetoplasmon modes. In the Weyl semimetal TaAs,
time-resolved second harmonic generation enabled us to reveal a new
photoinduced phase, and THz emission spectroscopy was used to provide
new insight into the circular photogalvanic effect.
Finally, we used
intense THz pulses to drive and coherently control structural dynamics
in the topological insulator Bi2Se3. Overall, our studies demonstrate
the utility of nonlinear optics in shedding new light on both static and
dynamic properties of topological materials.