Role of resident electrons in the manifestation of a spin polarization memory effect in Mn delta-doped GaAs heterostructures

The GaAs/InGaAs quantum wells with a ferromagnetic delta(Mn) layer in GaAs barrier demonstrate a set of interesting spin-related phenomena originating from Mn-hole interaction. One of such phenomena is a spin-memory effect which consists of Mn spin polarization induced by interaction with vicinity spin-polarized holes generated under the exposure by short circularly polarized light pulses. Here long Mn spin relaxation time (similar to 5 ns) allows preserving the spin polarization of the entire system. In the present paper the spin-memory effect investigation was carried out by analyzing the polarization kinetics of quantum-well photoluminescence in the pump-probe technique. It was shown that the photoluminescence circular polarization degree is strongly affected by the magnetic interaction of holes with Mn atoms prepolarized by the pump pulse. In the case of antiparallel Mn and hole polarizations, magnetic interaction leads to decrease of circular polarization degree as compared with single-pulse excitation (so called Delta P effect). Interestingly, the amplitude of hole-mediated Delta P effect is strongly affected by the concentration of resident electrons in the quantum well. The latter was shown to be caused by the specific compliance with selection rules for optical transitions with the participation of unpolarized resident electrons and spin-polarized holes affected by Mn-hole interaction.

Automated summary

The introduction of a ferromagnetic Mn layer in GaAs/InGaAs quantum wells leads to interesting spin-related phenomena such as spin-memory effect, which is induced by interaction between Mn and spin-polarized holes. Analysis of the polarization kinetics of quantum-well photoluminescence reveals a strong influence of magnetic interaction between holes and pre-polarized Mn atoms on circular polarization degree.