Ultrafast Optical and Low-frequency Spectroscopy of Semiconductor Nano-systems and Quantum Materials

Online Seminar
Date: Aug 18, 2020
Time: 10:00 AM (Local Time Germany)
Speaker: Jit Sarkar
Indian Institute of Science Education and Research Kolkata

Ultrafast spectroscopic studies are always instructive to understand the physics of light-matter interactions. Within a few pico-seconds after photo-excitation, the excess energy of photo-excited carriers get transferred to the lattice and eventually they attain a state of equilibrium, a process known as ultrafast thermalization. Electron-phonon (e-ph) coupling play a pivotal role in this process. The process of ultrafast thermalization was investigated in an assembly of ZnO nanorods and the analysis from the framework of Two Temperature Model (TTM) yields prolonged thermalization time due to reduced electron-phonon coupling at higher photo-excited carrier density [1].

Subsequently a brief discussion upon our observation about the presence of trap-assisted auger recombination along with conventional Shockley-Reed-Hall type recombination in indirect bandgap semiconductor will be presented [2].The second half of the talk will deal with the ultrafast and THz spectroscopy study in topological insulator thin films. Observation of coherent excitation of different phonon modes upon ultrafast optical excitation in topological insulator thin films will be discussed [3]. In the final section of the talk, I will show our preliminary results on THz conductivity of Pulsed Laser Deposition (PLD) grown topological insulator thin films. Granular nature of our PLD grown films yield non-Drude behaviour of optical conductivity and the same can be understood from the perspective of Drude-Smith model of ac conductivity of polycrystalline samples.

References:
[1]. Journal of Applied Physics, 124 (24), 243103.
[2]. The Journal of Physical Chemistry C, 123 (15), 10007-10012.
[3]. Applied Physics Letters, 106 (24), 241106.

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Meeting ID: 833 6749 4220