title: Ultrafast coherent electron transport in semiconductor quantum cascade structures.
abstract: Coherent electron transport is studied in an electrically driven quantum cascade structure. Ultrafast quantum transport from the injector into the upper laser state is investigated by midinfrared pump-probe experiments directly monitoring the femtosecond saturation and subsequent recovery of electrically induced optical gain. We demonstrate for the first time pronounced gain oscillations giving evidence for a coherent electron motion. The coexistence of a long dephasing time of quantum coherence and high Coulomb scattering rates in the injector points to the occurrence of scattering-induced coherence in electron transport.
authors.affiliation: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Eickemeyer
authors.forename: K
authors.initials: K
authors.lastname: Reimann
authors.forename: M
authors.initials: M
authors.lastname: Woerner
authors.forename: T
authors.initials: T
authors.lastname: Elsaesser
authors.forename: S
authors.initials: S
authors.lastname: Barbieri
authors.forename: C
authors.initials: C
authors.lastname: Sirtori
authors.forename: G
authors.initials: G
authors.lastname: Strasser
authors.forename: T
authors.initials: T
authors.lastname: Müller
authors.forename: R
authors.initials: R
authors.lastname: Bratschitsch
authors.forename: K
authors.initials: K
authors.lastname: Unterrainer