Ultrafast Broadband Electrodynamics of Carbon Nanostructures: From Inverted Dirac Fermions to Dark Excitons
This event is part of the Biophysics/Condensed Matter Seminar Series.
The dynamical and nonlinear properties of low-dimensional solids are fundamental in materials physics yet transformative in photonic technology today. Although there have been well-established static transport and linear optical properties in 2D graphenes and 1D carbon nanotubes, nonlinear transient phenomena and quantum processes at fs time scales have been much less addressed. Particularly, this field of research offers technological-relevant functions that are distinctly different from either bulk solids or simple molecules, e.g., dark states of 1D excitons and inverted Dirac fermions. The recent development of ultrafast laser sources and spectroscopy tools facilitates understanding these issues via resolving dynamic information often hidden in stationary measurements. In this talk, I will present two examples of applying them in exploring carbon nanostructures: (1) demonstration of stimulated near-infrared emission from population inversion of Dirac fermions in graphene; (2) discovery of the dark excitonic ground states in single-walled carbon nanotubes. Finally, I will also discuss technological implications and some other opportunities in this highly interdisciplinary field of research, which are enabled by the experimental concepts and capabilities revealed.
Jigang Wang is an assistant professor in the Department of Physics and Astronomy at Iowa State University and staff scientist in Ames laboratory of US department of Energy. He is an expert in experimental condensed matter physics, focusing on ultrafast laser spectroscopy and femtosecond quantum phenomena in nanostructures and strongly correlated electron materials. His current projects include ultrafast magnetism in correlated electrons, dynamics of iron pnictide superconductors, nonlinear optics in metamaterials, ultrabroadband electrodynamics in carbon nanotubes and graphenes. He is recipient of the NSF CAREER award. He received his Ph.D. from Rice University and joined Lawrence Berkeley National Laboratory as Physicist Postdoctoral Fellow.