Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session R18: Focus Session: Spin-Dependent Phenomena in Semiconductors - GaMnAs
2:30 PM–5:30 PM,
Wednesday, March 20, 2013
Sponsoring Units: GMAG DMP FIAP
Chair: John Peters, Northwestern University
Abstract ID: BAPS.2013.MAR.R18.1
Abstract: R18.00001 : Experimental observations of optical spin-transfer and spin-orbit torques in magnetic semiconductors*
2:30 PM–3:06 PM
Preview Abstract Abstract
(Charles University in Prague, Faculty of Mathematics and Physics)
The spin transfer torque (STT) is a non-relativistic phenomenon where angular momentum of spin polarized carriers electrically injected into a ferromagnet from an external polarizer is transferred to the magnetization . In the absence of an external polarizer a distinct phenomenon can occur in which carriers in a magnet under applied electric field develop a non-equilibrium spin polarization due to the relativistic spin-orbit coupling, resulting in a current induced spin-orbit torque (SOT) . We show, using the experimental data observed in the ferromagnetic semiconductor (Ga,Mn)As, that there exists optical counterparts of STT (OSTT)  and SOT (OSOT) . In OSTT a circularly polarized femtosecond pump laser pulse acts as the external polarizer and it induces a coherent magnetization precession due to the angular momentum transfer, in a direct analogy to the current induced STT . The absence of an external polarizer in OSOT corresponds to photo-carrier excitations which are independent of the polarization of the pump laser pulses and the phenomenon relies on spin-orbit coupling of non-equilibrium carriers, as in the case of the current induced SOT . Our work demonstrates the possibility to study the spin-transfer and spin-orbit torques on the sub-picosecond time-scales using the optical pump-and-probe experimental technique.\\[4pt]  A. Bratas et al., Nature Materials 11, 372 (2012).\\[0pt]  P. Nemec et al., Nature Physics 8, 411 (2012).\\[0pt]  N. Tesarova et al., submitted, arXiv: 1207.0307.
*This work was supported by the Grant Agency of the Czech Republic grant no. P204/12/0853.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2013.MAR.R18.1
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