title: Internal transitions of negatively charged magnetoexcitons and many body effects in a two-dimensional electron gas.
abstract: Internal transitions of quasi-two-dimensional, negatively charged magnetoexcitons ( X-) and their evolution with excess electron density have been studied in GaAs/AlGaAs quantum wells. In the dilute electron limit, due to magnetic translational invariance, the optically detected resonance spectra are dominated by bound-to-continuum bands in contrast to the negatively charged donor system D-, which exhibits strictly bound-to-bound transitions. With increasing excess electron density Landau-level filling factors nu<2 the X--like transitions are blueshifted; they are absent for nu>2. The blueshifted transitions are explained in terms of a new type of collective excitation---magnetoplasmons bound to a mobile valence band hole.
authors.affiliation: Department of Physics and Center for Advanced Photonic and Electronic Materials, SUNY Buffalo, Buffalo, New York 14260, USA.
authors.forename: H A
authors.initials: HA
authors.lastname: Nickel
authors.forename: T M
authors.initials: TM
authors.lastname: Yeo
authors.forename: A B
authors.initials: AB
authors.lastname: Dzyubenko
authors.forename: B D
authors.initials: BD
authors.lastname: McCombe
authors.forename: A
authors.initials: A
authors.lastname: Petrou
authors.forename: A Yu
authors.initials: AY
authors.lastname: Sivachenko
authors.forename: W
authors.initials: W
authors.lastname: Schaff
authors.forename: V
authors.initials: V
authors.lastname: Umansky