Spin-flip Raman scattering of the $\Gamma$-X mixed exciton in indirect band-gap (In,Al)As/AlAs quantum dots

TL;DR

This paper investigates the spin properties of indirect excitons in (In,Al)As/AlAs quantum dots using resonant spin-flip Raman scattering, revealing detailed g-factors and valley mixing effects relevant for quantum information applications.

Contribution

It introduces a method to study exciton spin states via Raman scattering, providing precise measurements of g-factors and insights into valley mixing mechanisms in indirect band-gap quantum dots.

Findings

Measured anisotropic hole and isotropic electron g-factors.

Identified spin-flip mechanisms and optical selection rules.

Correlated spin-flip intensity with $ ext{Γ}$-X valley mixing strength.

Abstract

The band structure of type-I (In,Al)As/AlAs quantum dots with band gap energy exceeding 1.63 eV is indirect in momentum space, leading to long-lived exciton states with potential applications in quantum information. Optical access to these excitons is provided by mixing of the $\Gamma$- and X-conduction band valleys, from which control of their spin states can be gained. This access is used here for studying the exciton spin-level structure by resonant spin-flip Raman scattering, allowing us to accurately measure the anisotropic hole and isotropic electron $g$ factors. The spin-flip mechanisms for the indirect exciton and its constituents as well as the underlying optical selection rules are determined. The spin-flip intensity is a reliable measure of the strength of $\Gamma$-X-valley mixing, as evidenced by both experiment and theory.