title: Observation of forbidden exciton transitions mediated by Coulomb interactions in photoexcited semiconductor quantum wells.
abstract: We use terahertz pulses to induce resonant transitions between the eigenstates of optically generated exciton populations in a high-quality semiconductor quantum well sample. Monitoring the excitonic photoluminescence, we observe transient quenching of the 1s exciton emission, which we attribute to the terahertz-induced 1s-to-2p excitation. Simultaneously, a pronounced enhancement of the 2s exciton emission is observed, despite the 1s-to-2s transition being dipole forbidden. A microscopic many-body theory explains the experimental observations as a Coulomb-scattering mixing of the 2s and 2p states, yielding an effective terahertz transition between the 1s and 2s populations.
authors.affiliation: Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005, USA.
authors.forename: W D
authors.initials: WD
authors.lastname: Rice
authors.forename: J
authors.initials: J
authors.lastname: Kono
authors.forename: S
authors.initials: S
authors.lastname: Zybell
authors.forename: S
authors.initials: S
authors.lastname: Winnerl
authors.forename: J
authors.initials: J
authors.lastname: Bhattacharyya
authors.forename: H
authors.initials: H
authors.lastname: Schneider
authors.forename: M
authors.initials: M
authors.lastname: Helm
authors.forename: B
authors.initials: B
authors.lastname: Ewers
authors.forename: A
authors.initials: A
authors.lastname: Chernikov
authors.forename: M
authors.initials: M
authors.lastname: Koch
authors.forename: S
authors.initials: S
authors.lastname: Chatterjee
authors.forename: G
authors.initials: G
authors.lastname: Khitrova
authors.forename: H M
authors.initials: HM
authors.lastname: Gibbs
authors.forename: L
authors.initials: L
authors.lastname: Schneebeli
authors.forename: B
authors.initials: B
authors.lastname: Breddermann
authors.forename: M
authors.initials: M
authors.lastname: Kira
authors.forename: S W
authors.initials: SW
authors.lastname: Koch