Dresden 2003 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
HL: Halbleiterphysik
HL 49: Poster II
HL 49.29: Poster
Donnerstag, 27. März 2003, 16:30–19:00, HSZ/P2
Mechanisms of Exciton Spin Relaxation in SC Quantum Dots — •Elena Tsistishvili1, Ralph von Baltz1, and Heinz Kalt2 — 1Institut für Theorie der Kond. Materie, Univ. Karlsruhe — 2Institut für Angewandte Physik, Univ. Karlsruhe
The discrete nature of the energy spectrum in semiconductor quantum dots (QD’s) leads to a strong suppression of spin relaxation which has been recently confirmed by Paillard et al. [1] for exciton states at low temperatures T<10 K. However, a rapid LO phonon–mediated decay occurs for T>30 K.
We propose a second order quasi-elastic interaction between the exciton ground state doublet and excited states via LO phonons [2]. Essential ingredients are: Anisotropic exchange splitting of the exciton, mismatch between the first excited exciton state and the LO phonon, and the LO phonon dispersion. Estimated decay times of a few tens of picoseconds at 100K, are in agreement with experiment[2].
At low temperatures a strong increase of the exciton–spin relaxation with magnetic field has been found [3,4]. Here, we propose a phonon – spin coupling mechanism due to an interplay of the exchange interaction and lattice deformations by acoustic phonons. Typically decay times are of the order of 3 ns at B=8T.
1. Paillard et al., Phys. Rev. Lett. 86, 1634 (2001).
2. Tsitsishvili et al., Phys. Rev. B 66, 161405(R), (2002).
3. Oka et al., Physica E 10, 315 (2001).
4. Verbin et al., phys. stat. sol. (b) 224, 545 (2001).