Volume 83, Number 4, August 2008
Article Number 47007
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 06 August 2008
EPL, 83 (2008) 47007
DOI: 10.1209/0295-5075/83/47007

Spin dynamics in the second subband of a quasi$\hbox{--} $two-dimensional system studied in a single-barrier heterostructure by time-resolved Kerr rotation

F. Zhang, H. Z. Zheng, Y. Ji, J. Liu and G. R. Li

State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences - P.O. Box 912, Beijing 100083, China

received 27 March 2008; accepted in final form 25 June 2008; published August 2008
published online 6 August 2008

Spin dynamics in the first and second subbands have been examined simultaneously by time resolved Kerr rotation in a single-barrier heterostructure of a 500 nm thick GaAs absorption layer. By scanning the wavelengths of the probe and pump beams towards the short wavelength in the zero magnetic field, the spin coherent time T21* in the $1{\rm st}$ subband E1 decreases in accordance with the D'yakonov-Perel' (DP) spin decoherence mechanism. Meanwhile, the spin coherence time T22* in the $2{\rm nd}$ subband E2 remains very low at wavelengths longer than 810 nm, and then is dramatically enhanced afterwards. At 803 nm, $T_{2}^{2*}(450\,{\rm ps})$ becomes ten times longer than $T_{2}^{1*}(50\,{\rm ps})$. A new feature has been discovered at the wavelength of 811 nm under the bias of $-0.3\,{\rm V}$ (807 nm under the bias of $-0.6\,{\rm V}$) that the spin coherence times ( T21* and T22* ) and the effective g* factors ( |g*(E1)| and |g*(E2)|) all display a sudden change, presumably due to the "resonant" spin exchange coupling between two spin opposite bands.

72.25.Fe - Optical creation of spin polarized carriers.
72.25.Dc - Spin polarized transport in semiconductors.
78.47.-p - Spectroscopy of solid state dynamics.

© EPLA 2008