Title: “Terahertz Spectroscopy of Photoexcited Carrier of Low Dimensional Materials”
Speaker: Dr. Srabani Kar, Department of Physics, IISER Tirupati
Date:12/01/2023, 05:30 PM , Ramanujan Hall
I shall present the photoexcited hot carrier dynamics of low (1D and 2D) dimensional nanomaterials using time-resolved terahertz spectroscopy. Time-resolved terahertz (THz) spectroscopy offers non-contact measurement of conductivity in unexcited and photoexcited states of materials along with the carrier relaxation dynamics. I shall discuss the unique negative and positive photoconductivity responses of single-layer graphene (SLG), and bilayer graphene (BLG) in the 0.5-2.5 THz after photo excitation with 800 nm 50 fs optical pump pulse. These dynamical responses were understood by applying semi-classical Boltzmann transport theory for the hot carriers. Next, I shall briefly present the studies on photoexcited semiconducting nanowires showing plasmonic responses in the terahertz range. The detailed investigations of the plasmon dynamics provide non-contact measurement of intrinsic mobilities and surface recombination rates of these nanowires, which are essential for any optoelectronic device applications.
Dr. Srabani Kar is an Inspire Faculty in the Department of Physics, Indian Institute of Science Education and Research (IISER), Tirupati, India. She earned Ph.D. in Physics in 2018 from the Indian Institute of Science (IISc), Bangalore on Time-resolved terahertz (THz) spectroscopy of low-dimensional materials in 2018. She then spent three years as a postdoctoral researcher at the University of Cambridge, UK, and a few months at the Indian Institute of Technology (IIT), Madras, India. Her research interests include ultrafast carrier dynamics of low-dimensional condensed matter systems, time-resolved terahertz spectroscopy, transient absorption spectroscopy, ultrafast light-matter interactions, and their applications in biomedical drug delivery into various cancer cells. She aims to establish a Terahertz research lab in India that will integrate fundamental physics, THz optoelectronic technology, and THz biomedical research.