Subject：Spin physics in colloidal nanocrystals
Speaker：Prof. Dmitri Yakovlev
Emcee：Prof Donghai Feng
Time：3:00pm, 12th Dec, 2018
Place：Science Building A814
Abstract：
A survey of our studies on spin-dependent phenomena in various colloidal semiconductor nanocrystals (NCs) measured mostly at low temperatures and in high magnetic fields up to 30 Tesla will be given. Several experimental techniques are used: polarized photoluminescence, spin-flip Raman scattering and pump-probe Faraday rotation with picosecond time resolution. Spin structure of neutral and charged excitons and spin dynamics, including coherent spin dynamics are investigated. We evaluate the exciton and carrier g-factors, characteristic spin relaxation times and receiving information on spin relaxation mechanisms, magneto-optical study provides information on type of NC charging and its dynamics. Circular polarization of photoluminescence induced by magnetic field allows us to identify the carrier left in the core of CdSe or CsPbBr3 NCs. Pump-probe time-resolved Faraday rotation experiments with additional prepump allows us to measure coherent spin dynamics of carriers in CdS NCs at room temperature and to study interplay between the negative and positive photocharging processes. Presence of the dangling bond spins on NC surface is confirmed experimentally by means of observation of the dangling bond spin polaron in CdSe NCs.
About the Speaker:
Prof. Dmitri R. Yakovlev was graduated from St. Petersburg Polytechnical University (1984) and got PhD (1988) and Doctor of Science (1998) degrees from Ioffe Physical-Technical Instutite. Since 1990 he is working in Germany, first in Würzburg University (1990-2002) then in TU Dortmund University (since 2002) and continues to be a staff of Ioffe institute. Since 2009, he is a professor in physic department in TU Dortmund. His current research interests are at the spin-dependent phenomena in semiconductor nanostructures, including epitaxially grown quantum wells and quantum dots, colloidal nanocrystals and perovskites, nonlinear optical phenomena on exciton resonances, magneto-optical studies in strong magnetic fields. He has published more than 350 articles in refereed journals and 9 book chapters, including Science –2, Nature Physics –3, Nature Photonics –2, Nature Nanotechnology –3, Nature Communications –5, Phys. Rev. Lett. –28. Owing to his great contribution in low-dimensional structure physics, he was elected as a fellow of the American Physical Society (APS) in 2009.
