We show that the so-called "trion line" in the absorption spectrum of doped quantum wells, comes from a singular many-body object, intrinsically wide in energy: the photocreated virtual exciton dressed by Coulomb and Pauli interactions with the well carriers. This understanding is supported by the spectra of circular dichroism obtained with a spin-polarized Fermi sea: the sharp edge on the low-energy side and the significant tail at high energies are well explained by these many-body effects, not by bound 3-body trions.
@article{arxiv.cond-mat/0409395,
title = {Many-body origin of the "trion line"},
author = {M. Combescot and J. Tribollet and G. Karczewski and F. Bernardot and C. Testelin and M. Chamarro},
journal= {arXiv preprint arXiv:cond-mat/0409395},
year = {2007}
}