Condensed Matter Physics

We are interested in the fundamental properties of electronic states and phonons in novel nanoscale materials and structures, including carbon nanotubes, graphene, hexagonal boron nitride, and the transition metal dichalcogenides. We examine the materials primarily through optical spectroscopy of the electronic transitions (absorption, scattering, photoluminescence spectroscopy) and of phonons (THz, IR, and Raman spectroscopy). We probe the dynamics of the system using femtosecond pump-probe and emission spectroscopy techniques across the spectral range. Issues of importance include understanding how quantum-confinement and heterostructuring influence the electronic and vibrational states in these materials. We have also found that these materials typically exhibit very strong many-body effects, leading to the formation of tightly bond excitons, as well as more complex states, such as charged excitons and biexcitons, and strong influence from substrate dielectric screening. In collaboration with theory groups, we are developing a fundamental understanding of these effects in various material systems.