Ultrafast Spectroscopy of Carbon Nanostructures: From Bosonic Excitons to Dirac Fermions

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Date/Time:Thursday, 11 Mar 2010 from 4:10 pm to 5:00 pm
Location:Physics 5
Channel:Condensed Matter Physics
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Prof. Jigang Wang (Iowa State University and Ames Laboratory, US DOE)

Understanding quasi-particle dynamics and pair correlation in nanostructures represents one of the major challenges now being posed for condensed matter and materials physics. The prominent examples are 1D bosonic excitation in single-walled carbon nanotubes (SWNTs) called excitons arising from strongly-bound electron and hole (e-h) pairs, and Dirac fermions in 2D graphene monolayer arising from the unique linear band dispersion. The amazing development of new ultrafast and ultra-broadband laser sources/spectroscopy techniques enabled from the far-IR, mid-IR to the visible spectrum opens many fascinating opportunities to study these systems. These new tools allow us to detect various quantum processes with resolution shorter than many key microscopic interactions responsible, providing in turn a powerful means to observe and disentangle various correlation effects, hidden in static experiments. In this talk, I will review some new ultrafast spectroscopy capabilities being developed in my group and present two examples of applying them in the exploration of quasi-particle correlation and dynamics in carbon nanostructures: (1) ultrafast 1D exciton formation and dynamics in SWNTs using time-resolved mid-IR intra-excitonic spectroscopy; (2) ultrafast three-particle coulomb scattering of extremely dense Dirac fermions. Finally, I will discuss some exciting new opportunities in the future enabled by the experimental concepts and capabilities revealed.