Seminar: Dong Yu, UC Davis
October 24 @ 11:00 am – 12:00 pm
Long and Fast Journey of Photogenerated Carriers in Topological Insulators
Abstract
The surface states of topological insulators (TIs) exhibit unusual Dirac dispersion relation, symmetry-protected transport against external perturbation, and helical spin texture. While electronic properties have been extensively studied in TIs, much less work has been carried out to understand how photogenerated carriers travel in these materials. Using spatially and temporally resolved photocurrent and photovoltage measurements, we observed surprising behaviors of photogenerated carriers in bulk-insulating TI Bi2Sb2-xSe3 nanoribbons. Photogenerated carriers appear to travel very long, up to hundreds of micrometers, before recombination, and very fast, orders of magnitude faster than that expected from band-edge carrier diffusion. The unusual behavior suggests superfluidic exciton condensation and is further supported by electric field-dependent photocurrent measurements.
Biography
Dong Yu is a Professor of Physics at the University of California, Davis. He completed his undergraduate degree at the University of Science and Technology of China and received his Ph.D. in Physics from the University of Chicago in 2005. Following a postdoctoral research position at Harvard University, he joined the Department of Physics and Astronomy at the University of California, Davis in 2008. His research group focuses on optoelectronic properties of nanomaterials. His current interests include studying topological materials and halide perovskites using a spatially and temporally resolved photocurrent method.
