A comprehensive study of excitonic complexes in high-quality GaAs quantum wells has been performed. The polarization-resolved photoluminescence results show exciton, biexciton, and trion emissions tuned by temper- ature, excitation power, and by an external magnetic field. Excitons and biexcitons show important differences in their dependence on the external field. While the Zeeman splitting of biexcitons depends monotonically on the magnetic field, with a nearly constant g-factor, the behaviour of the exciton energy splitting is nonmonotonic and includes an inversion of sign as a function of the magnetic field. More importantly, we observe that a trion resonance emerges at a finite magnetic field, and only appears at low laser excitation power and for σ⁺ polarization emission. The non-trivial dependence of the energy levels on the external magnetic field, together with the polarization selective trion emission, leads to an intricate exciton and trion dynamics, which can be reproduced by a set of coupled rate equations. Based on this theoretical approach, we show that a fast spin-flip process can lead to the spin-asymmetric emission, which reveals a contrasting spin-dynamics of excitonic complexes ruled by their charge.

已对高质量GaAs量子阱中的激子复合物进行了全面研究。偏振分辨的光致发光结果表明，激子，双激子和三重子的发射是通过温度，激发功率和外部磁场调节的。激子和双激子在对外部场的依赖性上显示出重要差异。尽管双激子的塞曼分裂单调取决于磁场，但具有几乎恒定的g因子，但激子能量分裂的行为是非单调的，并且包括符号随磁场的反转。更重要的是，我们观察到在有限的磁场下会产生三重共振，并且仅在低激光激发功率下且对于σ ⁺才会出现极化发射。能级对外部磁场的非平凡依赖，以及极化选择性三极子发射，导致复杂的激子和三极子动力学，可以通过一组耦合速率方程来再现。基于这种理论方法，我们证明了快速自旋翻转过程会导致自旋非对称发射，这揭示了受其电荷支配的激子复合物的自旋动力学对比。