B.S. 1978, Stanford University
Ph.D. 1982, UC Berkeley
Our research interest lie in understanding the dynamics of condensed matter systems, particularly in lower dimensional or nanoscale materials. Since the natural time scale for fundamental dynamical processes, whether it be the motion of electrons or of the nuclei, lies in the femtosecond time scale, one of the principal experimental tools that we employ in our investigations is the femtosecond modelocked laser. This tool provides us both with a means of achieving extremely high time resolution (~ 10^-13 s) and also permits us to achieve high optical intensities, thus allow us to exploit the nonlinear optical response of materials in these investigations.
A second important experimental tool in our program is the scanning tunneling microscope (STM). This instrument allows one direct access to the atomic scale structure of materials. Although not an inherently fast probe, it reveals important aspects of dynamics through the capability it offers to probe the initial and final states of materials with atomic precision. As we have also demonstrated in recent work, one may combine STM techniques with laser-based methods to achieve examine processes occurring on a very short time scale.
With these in-house capabilities we are presently examining problems that include the following:
- Probing electronic charge transport in photoexcited materials,
- including polaronic charge transport and the nature of charge transport in nanoscale materials such as quantum dots. This work relies on THz time-domain spectroscopy
- Examining the nature of energy transfer between atoms and molecules on surfaces by means of femtosecond laser excitation.
- nvestigation of surface processes, such as charging and adsorption,
- in a variety of environments by nonlinear laser spectroscopy; investigation of the nonlinear optical properties of nanostructures.
- STM studies of electronic properties of surfaces and adsorbate-covered surfaces.
Our research program forms part of different active multidisciplinary research programs at Columbia University: The Columbia Nanoscale Science and Engineering Center http://www.cise.columbia.edu/NSEC/index.html , the Columbia Institute on Environmental Molecular Science http://www.cise.columbia.edu/emsi/index.html, and the Materials Research Science and Engineering Center on Nanostructured Material http://www.cise.columbia.edu/mrsec/index.html
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|For a complete listing of publications see search engines like Spires and the like:
L. Bartels, F. Wang, D. Moeller, E. Knoesel and T. F. Heinz, "Real-Space Observation of Molecular Motion Induced by Femtosecond Laser Pulses," Science 305, 648 (2004).
F.. Wang, G. Dukovic, L. E. Brus, and T. F. Heinz, “Time-Resolved Fluorescence in Carbon Nanotubes and Its Implication for Radiative Lifetimes,” Phys. Rev. Lett. 92, 177401 (2004).
M.Y. Sfeir ,F. Wang ,L.M. Huang, C.C. Chuang, J. Hone, S.P. O'Brien, T.F. Heinz, L.E. Brus, “Probing Electronic Transitions in Individual Carbon Nanotubes by Rayleigh Scattering,” Science 306, 1540 (2004).
F. Wang, G. Dukovic, L. E. Brus, and T. F. Heinz, “The Optical Resonances in Carbon Nanotubes Arise from Excitons,” Science 308, 838 (2005).
G. Dukovic, F. Wang, D. H. Song, M. Y. Sfeir, T. F. Heinz, and L. E. Brus, “Structural Dependence of Excitonic Optical Transitions and Band-Gap Energies in Carbon Nanotubes,” Nano Lett. 5, 2314 (2005).
F. Wang, M. Y. Sfeir, L. Huang, X. M. H. Huang, Y. Wu, J. Kim, J. Hone, S. O'Brien, L. E. Brus, and T. F. Heinz, “Interactions between Individual Carbon Nanotubes Studied by Rayleigh Scattering Spectroscopy,” Phys. Rev. Lett. 96, 167401 (2006).
F. Wang, Y. Wu, M. S. Hybertsen, and T. F. Heinz, “Auger Recombination of Excitons in One-Dimensional Nanostructures,” Phys. Rev. B 73, 245424 (2006).
M. Y. Sfeir, T. Beetz, F. Wang, L. Huang, X. M. H. Huang, M. Huang, J. Hone, S. P. O’Brien, J. A. Misewich, T. F. Heinz, L. Wu, Y. Zhu, and L. E. Brus, “Optical Spectroscopy of Individual Single-Walled Carbon Nanotubes of Defined Chiral Structure,” Science 312, 554 (2006).