Spin-triplet negatively charged excitons in GaAs quantum wells

Abstract
We observe magnetic-field-induced transitions in the interband optical spectra of GaAs quantum wells with a small excess electron density. Their strengthening with excess electron density, in addition to their light polarization dependence, demonstrate that these correspond to (excited) spin-triplet states of the negatively charged exciton. The second-electron binding energy of both singlet and triplet X strengthens with field.