Dr. Dong Yu from University of California, Davis will be talking about " Highly mobile excitons in hybrid halide perovskites and topological insulators".
Abstract: Excitons, electron-hole pairs bound by Coulomb interaction, are important quasi-particles that have profound effects on the optoelectronic properties of semiconductor materials. Excitons are often regarded as more localized than free carriers. In this talk, I will show that excitons can be significantly more mobile than free charge carriers in certain materials. Two case studies will be presented based on our recent experimental work using photocurrent imaging. The first is hybrid inorganic-organic lead halide perovskites, where the exciton scattering with optical phonons is suppressed compared to free charge carriers because of the dipolar nature of excitons . The second case is topological insulators. We observed millimeter-long transport of photogenerated carriers, which can be understood by superfluidic exciton condensation . Highly non-local excitons may find novel applications in energy harvesting and quantum computing.
 L. McClintock, R. Xiao, Y. Hou, C. Gibson, H.C. Travaglini, D. Abramovitch, L.Z. Tan, R.T. Senger, Y. Fu, S. Jin, and D. Yu, "Temperature and Gate Dependence of Carrier Diffusion in Single Crystal Methylammonium Lead Iodide Perovskite Microstructures," Journal of Physical Chemistry Letters, 11, 1000 (2020).
 Y. Hou, R. Wang, R. Xiao, L. McClintock, H. Clark Travaglini, J. Paulus Francia, H. Fetsch, O. Erten, S.Y. Savrasov, B. Wang, A. Rossi, I. Vishik, E. Rotenberg, and D. Yu, "Millimetre-long transport of photogenerated carriers in topological insulators," Nature Communications, 10, 5723 (2019). 10.1038/s41467-019-13711-3