Unraveling Photoinduced Spin Dynamics in the Topological Insulator Bi2Se3

作     者：M. C. Wang S. Qiao Z. Jiang S. N. Luo J. Qi 

作者机构：The Peac Institute of Multiscale Sciences Chengdu Sichuan 610031 People’s Republic of China Key Laboratory of Advanced Technologies of Materials Ministry of Education Southwest Jiaotong University Chengdu Sichuan 610031 People’s Republic of China State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 People’s Republic of China School of Physical Science and Technology ShanghaiTech University Shanghai 200031 People’s Republic of China School of Physics Georgia Institute of Technology Atlanta Georgia 30332 USA 

出 版 物：《Physical Review Letters》 (Phys Rev Lett)

年 卷 期：2016年第116卷第3期

页      面：036601-036601页

核心收录：

学科分类：07[理学] 0702[理学-物理学] 

基　　金：China 1000-Young Talents Plan U.S. Department of Energy, USDOE, (DE-FG02-07ER46451) National Natural Science Foundation of China, NSFC, (10979021, 11027401, 11174054, 11227902, 11304338) Chinese Academy of Sciences, CAS, (XDB04010100) Ministry of Science and Technology of the People's Republic of China, MOST Helmholtz Association National Key Research and Development Program of China, NKRDPC, (2011CB921800) 

主　　题：Electric polarization Surface states Topological insulators Kerr effect Reflectivity 

摘      要：We report on a time-resolved ultrafast optical spectroscopy study of the topological insulator Bi2Se3. We unravel that a net spin polarization cannot only be generated using circularly polarized light via interband transitions between topological surface states (SSs), but also via transitions between SSs and bulk states. Our experiment demonstrates that tuning photon energy or temperature can essentially allow for photoexcitation of spin-polarized electrons to unoccupied topological SSs with two distinct spin relaxation times (∼25 and ∼300 fs), depending on the coupling between SSs and bulk states. The intrinsic mechanism leading to such distinctive spin dynamics is the scattering in SSs and bulk states which is dominated by Eg2 and A1g1 phonon modes, respectively. These findings are suggestive of novel ways to manipulate the photoinduced coherent spins in topological insulators.