Spectroscopy for the Masses (of Carbon Atoms)

Who: Eric Heller, Harvard University
Tuesday, May 3, 2016 - 4:00pm to 5:30pm
Chevron 150
219 Parkman ave

For some reason, the theory of the interaction of light with graphene, nanotubes, graphite, etc. got off on the wrong foot 15 years ago. The established approaches were cast aside without mention. We have developed and used the correct theory for the first time, based on light-matter perturbation and the Born-Oppenheimer approximation. With 12 years of experimental data on graphene to work with, the story of the interaction of graphene with light has now changed dramatically. Qualitatively new processes are found, such as a continuum of electron-hole pair transitions possible at a single laser frequency, assisted by the linear dispersion of the Dirac cones famous in graphene. These explain the large excess UV light absorption in graphene over what was supposed to be the “universal” constant value, the immediate emission of seemingly thermalized light in pulsed femtosecond experiments, and all major aspects of the Raman spectrum, including the enigmatic brightness of a dominant (but normally dim) overtone band.