Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 55: Quantum Dots and Wires, Optical Properties IV: Spin

HL 55.7: Talk

Thursday, March 25, 2010, 15:30–15:45, H14

Spin-flip Raman scattering in InGaAs/GaAs quantum dots — •Jörg Debus¹, V. F. Sapega², D. R. Yakovlev^1,2, and M. Bayer¹ — ¹Experimentelle Physik II, Technische Universität Dortmund, 44227 Dortmund, Germany — ²A. F. Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia

Strong spin-flip Raman scattering (SFRS) from self-assembled n-doped InGaAs/GaAs quantum dots as well as from an undoped sample has been observed in external magnetic fields up to 10 T. In both cases the SFRS exhibits a strong dependence on the geometry of the experiment. The predominant Raman signal is attributed to a spin-flip of a resident electron induced by a photocreated exciton.

The magnetic field dependencies of the electronic Raman shift, measured in Voigt- and tilted Faraday-geometry, demonstrate similar slopes (|g|_||^e ≈ 0.62 and |g|_⊥^e ≈ 0.54), but tend to different Raman shifts at zero magnetic field. In tilted Faraday-geometry the Raman shift tends to δ=0.4 cm⁻¹, it depends also on the optical excitation energy as well as on the annealing temperature of the samples. The offset at B=0 T can be related to excitonic exchange interaction and to additional nuclear magnetic fields acting on the resident electrons. At B=10 T the electronic spin-flip shift is larger in tilted Faraday- than in Voigt-geometry, which originates from an electron g factor anisotropy.

The electron g factor dispersion has been measured across the emission band of the inhomogeneously broadened quantum dot ensemble.