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[1], graphane (hydrogen functionalized graphene)[2], carbon nanotubes[3] and transition metal dichalcogenides[4] 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[5].
[1] 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)
[2] Srabani Kar, Dipti R. Mohapatra and A.K. Sood, Tunable terahertz photoconductivity of hydrogen functionalized graphene using optical pump-terahertz probe spectroscopy, Nanoscale (2018)
[3] Srabani Kar and A.K. Sood, Ultrafast terahertz photoresponse of single and double- walled carbon nanotubes: Optical pump-terahertz probe spectroscopy. (2018)
[4] 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)
[5] K.P. Mithun et.al (2019)
