title: Unraveling Photoinduced Spin Dynamics in the Topological Insulator Bi(2)Se(3).
abstract: We report on a time-resolved ultrafast optical spectroscopy study of the topological insulator Bi_{2}Se_{3}. 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 E_{g}^{2} and A_{1g}^{1} phonon modes, respectively. These findings are suggestive of novel ways to manipulate the photoinduced coherent spins in topological insulators.
authors: 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.
authors: M C
authors: MC
authors: Wang
authors: 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.
authors: S
authors: S
authors: Qiao
authors: School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
authors: Z
authors: Z
authors: Jiang
authors: 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.
authors: S N
authors: SN
authors: Luo
authors: 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.
authors: J
authors: J
authors: Qi