Internal transitions of two-dimensional charged magneto-excitons X−: theory and experiment

Internal spin-singlet and spin-triplet transitions of charged excitons X− in magnetic fields in quantum wells have been studied experimentally and theoretically. The allowed X− transitions are photoionizing and exhibit a characteristic double-peak structure, which reflects the rich structure of the magnetoexciton continua in higher Landau levels (LLs). We discuss a novel exact selection rule, a hidden manifestation of translational invariance, that governs transitions of charged mobile complexes in a magnetic field.