Ultrafast and Ultrabroadband Electrodynamics in Low Dimensions: From Dark Bosons to Dirac Fermions

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Date/Time:Thursday, 18 Oct 2012 from 4:10 pm to 5:00 pm
Location:Physics 0005
Phone:515-294-5441
Channel:Colloquium
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Jigang Wang, Ames Laboratory of US DoE and Department of Physics & Astronomy, Iowa State University.

The dynamical and nonlinear properties of low-dimensional solids are fundamental in condensed matter/materials physics yet most transformative in photonic technology today. Although there have been well-established static transport and linear optical properties in 2D graphenes and 1D carbon nanotubes, femtosecond (10^-15s, fs) transient phenomena have been much less addressed. This is despite of the fact that this field of research offers technological-relevant functions that are distinctly different from either bulk solids or simple molecules, e.g., ultrafast population inversion, optical gain, high-speed all-optical modulation, infrared photo-detection. The recent amazing development of ultrafast laser sources and spectroscopy tools from terahertz to ultra-violet facilitates understanding these issues via resolving broadband, dynamic information often hidden in stationary measurements. In this talk, I will apply them to solve two of the most puzzling questions in the field of carbon nanostructures: (1) How to access dark excitonic Bosons in single-walled carbon nanotubes? (2) Can one create an inverted Dirac fermion states exhibiting optical gain in graphenes? Finally, I will also discuss some other opportunities, that are enabled by the experimental concept and capability revealed, including strongly correlated electrons, meta-materials, heavy fermions and non-conventional superconductors.

Brief bio: Jigang Wang is an assistant professor in the Department of Physics and Astronomy at Iowa State University and staff scientist in the Ames laboratory of the U.S. Department of Energy. He received his Ph.D. from Rice University at 2005 with Jun Kono and joined Lawrence Berkeley National Laboratory as Postdoctoral under Daniel Chemla. He is working in experimental condensed matter physics, focusing on femtosecond laser spectroscopy and ultrafast transient phenomena in nanostructures and quantum materials. His current projects include ultrafast magnetism in strongly correlated electrons, ultrafast dynamics of iron pnictide superconductors, nonlinear optics in metamaterials, ultrabroadband electrodynamics in carbon nanotubes and graphenes. He is recipient of the NSF CAREER award and LAS Award for Early Achievement in Research at Iowa State University.