T Grange et al 2007 New J. Phys. 9 259 doi:10.1088/1367-2630/9/8/259
Singlet and triplet polaron relaxation in doubly charged self-assembled quantum dots
T Grange1,6, E A Zibik2, R Ferreira1, G Bastard1, B A Carpenter2, P J Phillips3, D Stehr4, S Winnerl4, M Helm4, M J Steer5, M Hopkinson5, J W Cockburn2, M S Skolnick2 and L R Wilson2
Show affiliationsPolaron relaxation in self-assembled InAs/GaAs quantum dot samples containing 2 electrons per dot is studied using far-infrared, time-resolved pump–probe measurements for transitions between the s-like ground and p-like first excited conduction band states. Spin–flip transitions between singlet and triplet states are observed experimentally in the decay of the absorption bleaching, which shows a clear biexponential dependence. The initial fast decay (~30 ps) is associated with the singlet polaron decay, while the decay component with the longer time constant (~5 ns) corresponds to the excited state triplet lifetime. The results are explained by considering the intrinsic Dresselhaus spin–orbit interaction, which induces spin–flip transitions by acoustic phonon emission or phonon anharmonicity. We have calculated the spin–flip decay times, and good agreement is obtained between the experiment and the simulation of the pump–probe signal. Our results demonstrate the importance of spin-mixing effects for intraband energy relaxation in InAs/GaAs quantum dots.
- PACS
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71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
- Subjects
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Condensed matter: electrical, magnetic and optical
- Dates
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Issue 8 (August 2007)
Received 9 May 2007
Published 10 August 2007
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Singlet and triplet polaron relaxation in doubly charged self-assembled quantum dots
T Grange et al 2007 New J. Phys. 9 259
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