Accepted : Magnetic and power tuning of spin-asymmetric multiple excitons in a GaAs quantum well

Naranjo, A., Bragança¸ H., Jacobsen, G. M., de Morais, R. R. O., Dias, I. F. L., Quivy, A. A., Marques, G. E., Lopez-Richard, V. and Teodoro, M. D.

Physica E: Low-dimensional Systems and Nanostructures (nov 2020)
DOI :  10.1016/j.physe.2020.114599

Abstract

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.