Freiburg 2019 – wissenschaftliches Programm

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FM: Fall Meeting

FM 63: Poster: Enabling Technologies: Quantum Materials, Quantum Dots, Quantum Wires, Point Contacts and Superconducting Systems

FM 63.1: Poster

Mittwoch, 25. September 2019, 16:30–18:30, Tents

Light-driven nuclei thermodynamics in bulk GaAs and (In,Ga)As/GaAs quantum dots — •Pavel Sokolov¹, Mikhail Petrov², Kirill Kavokin², Maria Kuznecova², Sergey Verbin², Dirk Reuter³, Andreas D. Wieck⁴, Dmitri Yakovlev^1,5, and Manfred Bayer^1,5 — ¹Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund, Germany — ²Spin Optics Laboratory, Saint Petersburg State University, 198504 St. Petersburg, Russia — ³Department Physik Universität Paderborn, D-33098 Paderborn, Germany — ⁴Angewandte Festkörperphysik Ruhr-Universität Bochum, D-44780 Bochum, Germany — ⁵Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia

We study experimentally the optical cooling dynamics of nuclei located inside the donor orbit in n-doped GaAs and (In,Ga)As/GaAs quantum dots and show that at slow modulation of excitation polarization (∼1 s) a noticeable Overhauser field can be observed. The initial cooling rate is strongly dependent on the direction of the external magnetic field with respect to initial electron polarization direction ± S₀. The lowest spin temperature in n-GaAs, Θ_N=1.5 mK was achieved in this work after cooling for T_mod=1 s. For the microstructure with (In,Ga)As/GaAs quantum dots, the achieved spin temperature is one order of magnitude lower than in n-GaAs: Θ_N=0.1 mK. Using the implemented technique allows us to verify the polarization of nuclear spins in the external magnetic field in the desired spin polarization state in two different types of semiconductor microstructures studied in this work.