title: Collective excitation of Rydberg-atom ensembles beyond the superatom model.
abstract: In an ensemble of laser-driven atoms involving strongly interacting Rydberg states, the steady-state excitation probability is usually substantially suppressed. In contrast, here we identify a regime in which the Rydberg excited fraction is enhanced by the interaction. This effect is associated with the buildup of many-body coherences induced by coherent multiphoton excitations between collective states. The excitation enhancement should be observable under currently existing experimental conditions and may serve as a direct probe for the presence of coherent multiphoton dynamics involving collective quantum states.
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Gärttner
authors.affiliation: Physikalisches Institut, Universität Heidelberg, Im Neuenheimerfeld 226, 69120 Heidelberg, Germany.
authors.forename: Shannon
authors.initials: S
authors.lastname: Whitlock
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany and Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Straße 38, 01187 Dresden, Germany.
authors.forename: David W
authors.initials: DW
authors.lastname: Schönleber
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Evers