Insights into Quantum Materials by Ultrafast Spectroscopy
Ultrafast lasers offer unique possibilities to control and probe transient processes in quantum materials. Following photoexcitation by a femtosecond laser pulse, the carrier dynamics includes many important processes like thermalization, energy relaxation, exciton formation and spin dynamics which are impacted by dimensionality. Their understanding is crucial not only for many optoelectronic applications, but also to gain a deeper understanding of physical processes in materials. My talk will discuss some of our recent work on the dynamics of optical pump induced photocarriers in single and bilayer graphene, graphane (hydrogen functionalized graphene), carbon nanotubes and transition metal dichalcogenides as probed by time-resolved terahertz spectroscopy.
Time permitting, the second part of my talk will address ultrafast dynamics in recently discovered 3D analogues of graphene (massless Dirac Fermions in 3D), namely Weyl and Dirac semimetals- NbAs, TaAs and Cd3As2.
 Srabani Kar, Van Luan Nguyen, Dipti R. Mohapatra, Young Hee Lee and A.K. Sood, Ultrafast Spectral-response of Bilayer Graphene: Optical pump-Terahertz Probe Spectroscopy and Theory. ACS Nano DOI: 10.1021/acsnano.7b08555 (2018)
 Srabani Kar, Dipti R. Mohapatra and A.K. Sood, Tunable terahertz photoconductivity of hydrogen functionalized graphene using optical pump-terahertz probe spectroscopy, Nanoscale (2018)
 Srabani Kar and A.K. Sood, Ultrafast terahertz photoresponse of single and double- walled carbon nanotubes: Optical pump-terahertz probe spectroscopy. (2018)
 S. Kar, Yang Su, Rahul Nair, A.K. Sood, Probing photoexcited carriers in MoS2 laminate by time resolved optical pump terahertz probe spectroscopy. ACS Nano 9, 12004 (2015)
 K.P. Mithun et.al (2019)
January 07, 2019
Professor Satyajit Mayor, Director, National Centre for Biological Sciences, (TIFR), Bangalore, India
Life at the Cell's edge; the active membrane bilayer
The plasma membrane of the living cell acts as an interface between the cell and its external milieu and serves as a dynamic conduit for information transduction. It is composed of membrane lipids and protein in the form of a fluid bilayer. At the same time the cell membrane is a highly organized system, with specific components in states that are far away from chemical equilibrium. Imaging the local organization of membrane components suggeststhat the active mechanics of dynamic cortical actin filaments facilitates the creation of these states, resulting in active actin-membrane composite, The dynamic actin participates in generating localized domains in the membrane. Signalling receptors embedded in the membrane regulatethe molecular machinery necessary for the generation of the dynamic actin.This has functional consequences for membrane receptor function and provides insights into how this active organization may inform the generation of a living cell membrane.