# Role of excited states in the dynamics of excitons and their spins in diluted magnetic semiconductors

## TL;DR

This paper demonstrates that excited states significantly influence exciton and spin dynamics in diluted magnetic semiconductors, with quantum kinetic effects enabling population of dark states even below resonance conditions.

## Contribution

It reveals the importance of exciton-impurity correlations and quantum kinetic theory in understanding exciton dynamics beyond the independent-particle approximation.

## Key findings

- Higher exciton states are populated below the resonance magnetic field.
- Exciton-impurity correlations bridge energy gaps of a few meV.
- Significant spin transfer to optically dark 2p exciton states.

## Abstract

We theoretically investigate the impact of excited states on the dynamics of the exciton ground state in diluted magnetic semiconductor quantum wells. Exploiting the giant Zeeman shift in these materials, an external magnetic field is used to bring transitions between the exciton ground state and excited states close to resonance. It turns out that, when treating the exciton dynamics in terms of a quantum kinetic theory beyond the Markov approximation, higher exciton states are populated already well below the critical magnetic field required to bring the exciton ground state in resonance to an excited state. This behavior is explained by exciton-impurity correlations that can bridge energy differences on the order of a few meV and require a quantum kinetic description beyond the independent-particle picture. Of particular interest is the significant spin transfer toward states on the optically dark $2p$ exciton parabola which are protected against radiative decay.