Optically controlled spin-polarization memory effect on Mn delta-doped heterostrucutres

TL;DR

This study demonstrates that Mn ions in InGaAs/GaAs heterostructures can act as optically controlled spin-memory, influencing carrier spin polarization and relaxation dynamics, with effects observable via time-resolved photoluminescence.

Contribution

It reveals the spin-memory effect of Mn ions in heterostructures and how optical excitation can control this interaction, a novel insight into spin dynamics in such materials.

Findings

Mn ions act as a spin-memory affecting carrier polarization.

Optical control of Mn spin state is demonstrated.

Spin effects diminish with time delay and temperature.

Abstract

We investigated the dynamics of the interaction between spin-polarized photo-created carriers and Mn ions on InGaAs/GaAs:Mn structures. The carriers are confined in an InGaAs quantum well and the Mn ions come from a Mn delta-layer grown at the GaAs barrier close to the well. Even though the carriers and the Mn ions are spatially separated, the interaction between them is demonstrated by time-resolved spin-polarized photoluminescence measurements. Using a pre-pulse laser excitation with an opposite circular-polarization clearly reduces the polarization degree of the quantum-well emission for samples where a strong magnetic interaction is observed. The results demonstrate that the Mn ions act as a spin-memory that can be optically controlled by the polarization of the photocreated carriers. On the other hand, the spin-polarized Mn ions also affect the spin-polarization of the subsequently created carriers as observed by their spin relaxation time. These effects fade away with increasing time delays between the pulses as well as with increasing temperatures.