Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 7: Quantum dots and wires: Optical properties I
HL 7.11: Vortrag
Montag, 27. März 2006, 12:45–13:00, POT 151
Spin coherence in spherical CdS quantum dots — •P. Nahalkova1,2, D. Sprinzl1, P. Nemec1, P. Maly1, V. N. Gladilin2, and J. T. Devreese2 — 1Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2, Czech Republic — 2Universiteit Antwerpen, Universiteitsplein 1, B-2610 Antwerpen, Belgium
Spin coherence in quasi-spherical CdS quantum dots (QDs) in a glass matrix has been investigated. Time-resolved differential transmission experiments were performed to measure the decay of the degree of circular (linear) polarization DCP (DLP). We show that due to the nearly spherical shape of our QDs, the properties of DCP and DLP differ considerably from those of the most often investigated pyramidal self-assembled QDs. Namely, the electron spin relaxation time of ∼ 10 ns can be deduced from the DCP decay. The DCP dynamics measured on ns timescale can be explained well by intralevel exciton transitions with electron spin flip, driven by the electron-hole exchange interaction and assisted by two LO phonons. Two-phonon processes contribute significantly also to exciton transitions without electron spin flip, which are manifested in DCP and DLP dynamics on ps timescale. We also discuss the influence of attractive interaction between electron-hole pairs on DCP and DLP. This work was supported by the Ministry of Education of the Czech Republic in the framework of the research plan MSM 0021620834 and the research centre LC510, as well as by the Bijzonder Onderzoeksfonds of the Universiteit Antwerpen, BOF NOI UA 2004, IUAP (Belgium), and the European Commission SANDiE Network of Excellence, contract No. NMP4-CT-2004-500101.