题 目：Spin phenomena in colloidal semiconductor nanocrystals
报告人：Prof. Dmitri R. Yakovlev
主持人：冯东海研究员
时 间：2020年10月29日16:00
地 点：腾讯会议 ID：975 896 284
报告人简介：
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 550 articles in refereed journals and 8 book chapters, including: Science – 2, Nature Physics – 3, Nature Nanotechnology – 4, Nature Photonics – 2, Nature Communications – 7, Phys. Rev. Lett. – 28, Phys. Rev. X – 3, Nano Lett. – 9, Phys. Rev. B – 181. Owing to his contribution in low-dimensional structure physics, he was elected as a fellow of the American Physical Society (APS) in 2009.
报告内容简介：
A survey of our studies on spin-dependent phenomena in various colloidal 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. Additionally, 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 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. We find experimentally that the surface of diamagnetic CdSe nanocrystals and nanoplatelets has paramagnetic spins which controls exciton polarization and recombination dynamics of the dark excitons. Also effects provided by the presence of magnetic Mn ions, which strongly enhances the magneto-optical properties of NCs will be discussed.