Localized charged magnetoexcitons in 2D systems

We performed a detailed theoretical study of localization of spin-singlet $X_s ^-$ and spin-triplet $X_t ^-$ negatively charged excitons on isolated charged donors $D^+$ located at various distances $L$ from the heteroboundary of a Quantum Well (QW). Our results show that the parent bright singlet state $X_s ^-$ remains always bound. In contrast, the dark $X_{td} ^-$ and bright $X_{tb} ^-$ triplet states survive only for sufficiently large distances $L$ to the donor ion $D^+$. In the presence of the $D^+$ the dark triplet acquires finite oscillator strengths. We also found several new bound $X^-$ states, some of which have surprisingly large oscillator strengths. We showed that shake-up processes are strictly prohibited in magneto-photoluminescence of free charged excitons and only become allowed in the presence of a $D^+$ or other symmetry-breaking mechanisms. Our results show that the main magneto-PL peaks of free and donor bound charged excitons may exhibit very similar features while the shake-up processes in PL are symmetry-breaking signatures.