Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 23: Spintronics: Excitons and local spins (with MA/TT)
HL 23.2: Vortrag
Dienstag, 17. März 2015, 09:45–10:00, ER 270
Spin properties of the indirect exciton in indirect band-gap (In,Al)As/AlAs quantum dot ensembles — •Jörg Debus1, Victor F. Sapega2, Timur S. Shamirzaev3, Daniel Dunker1, Evgeny L. Ivchenko2, Dmitri R. Yakovlev1,2, and Manfred Bayer1,2 — 1Experimentelle Physik 2, TU Dortmund, Dortmund, Germany — 2Ioffe Physical-Technical Institute, St. Petersburg, Russia — 3Institute of Semiconductor Physics, Novosibirsk, Russia
The band structure of type-I (In,Al)As/AlAs quantum dots with band gap energy exceeding 1.63 eV is indirect in momentum space, leading to long-lived exciton states with potential applications in quantum information. Optical access to these excitons is provided by mixing of the Γ- and X-conduction band valleys. We report on spin properties of the indirect exciton studied by time-resolved photoluminescence (TRPL) and resonant spin-flip Raman scattering (SFRS) [1-3]. The SFRS characterizes the Γ-X-valley electron state mixing, provides access to the fine structure of the indirect exciton and enables the preparation of its spin states as well as the determination of the spin-flip mechanisms. From the TRPL we evaluate very long longitudinal spin relaxation times (200 µs at 4 T and 1.8 K) that are rather robust against temperature changes. The temporal evolution of the circular polarization degree of the photoluminescence moreover changes its sign in the µs-range thus hinting at dark and bright indirect excitons contributing by their different spin dynamics. [1] T. S. Shamirzaev et al., Phys. Rev. B 84, 155318 (2011). [2] D. Dunker et al., Appl. Phys. Lett. 101, 142108 (2012). [3] J. Debus et al., Phys. Rev. B 90, 125431 (2014).