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

TL;DR

This study investigates how resident electrons influence the spin polarization memory effect in Mn delta-doped GaAs heterostructures, revealing the importance of electron concentration and proposing a photoluminescence method for analysis.

Contribution

It demonstrates the role of resident electrons in the spin polarization memory effect and introduces a photoluminescence technique to measure this effect and Mn spin relaxation time.

Findings

The circular polarization degree of photoluminescence is strongly affected by Mn spin polarization.

The amplitude of the delta P-effect depends on resident electron concentration.

The effect decreases with decreasing spatial separation between Mn layer and quantum well.

Abstract

The spin-memory effect in the GaAs / InGaAs heterostructures with $\delta$<Mn> layer in GaAs barrier have been investigated. The effect consists in spin polarization of Mn atoms due to interaction with photogenerated spin-polarized holes. The investigation of the effect was carried out by analyzing the polarization of the probe photoluminescence pulse in the pump-probe technique. It was shown that the circular polarization degree of probe pulse generated photoluminescence is strongly affected by the interaction of hole spins with spins of Mn atoms polarized by the pump pulse. The latter leads to decrease of circular polarization degree as compared with single pulse excitation ($\delta P$ effect). The amplitude of $\delta P$-effect is most strongly affected by the concentration of resident electrons in the quantum well which is believed to be due the specific compliance with selection rules for optical transition with the participation of unpolarized resident electrons. The rest of the sample's parameters including the spatial separation between $\delta$<Mn> layer and InGaAs quantum well ($d_s$) have a minor effect on the $\delta P$ value which leads to a paradoxical situation of decreasing $\delta P$-effect with the decrease of $d_s$. The proposed experimental technique consisting in creating the significant concentration of resident electrons in the QW may serve as a reliable photoluminescence method determining the strength of this effect as well as the Mn spin relaxation time in a particular nanostructure.