Spin coherence of a two-dimensional electron gas induced by resonant excitation of trions and excitons in CdTe/(Cd,Mg)Te quantum wells

TL;DR

This study investigates how long-lived spin coherence in a 2D electron gas within CdTe/(Cd,Mg)Te quantum wells is generated through resonant excitation of excitons and trions, combining experimental Kerr rotation measurements with theoretical analysis.

Contribution

It provides a comprehensive experimental and theoretical analysis of spin coherence generation mechanisms in 2DEG, highlighting the roles of excitons and trions.

Findings

Good agreement between experiment and theory.

Resonant excitation of trions and excitons effectively generates spin coherence.

Multiple mechanisms, including direct trion creation and electron-exciton exchange, contribute to spin coherence.

Abstract

The mechanisms for generation of long-lived spin coherence in a two-dimensional electron gas (2DEG) have been studied experimentally by means of a picosecond pump-probe Kerr rotation technique. CdTe/(Cd,Mg)Te quantum wells with a diluted 2DEG were investigated. The strong Coulomb interaction between electrons and holes, which results in large binding energies of neutral excitons and negatively charged excitons (trions), allows one to address selectively the exciton or trion states by resonant optical excitation. Different scenarios of spin coherence generation were analyzed theoretically, among them the direct trion photocreation, the formation of trions from photogenerated excitons and the electron-exciton exchange scattering. Good agreement between experiment and theory is found.