title: Observation of a red-blue detuning asymmetry in matter-wave superradiance.
abstract: We report the first experimental observation of strong suppression of matter-wave superradiance using blue-detuned pump light and demonstrate a pump-laser detuning asymmetry in the collective atomic recoil motion. In contrast to all previous theoretical frameworks, which predict that the process should be symmetric with respect to the sign of the detuning of the pump laser from the one-photon resonance, we find that for condensates the symmetry is broken. With high condensate densities and red-detuned pump light the distinctive multiorder, matter-wave scattering pattern is clearly visible, whereas with blue-detuned pump light superradiance is strongly suppressed. However, in the limit of a dilute atomic gas symmetry is restored.
authors.affiliation: Physics Laboratory, National Institute of Standards & Technology, Gaithersburg, MD 20899, USA.
authors.forename: L
authors.initials: L
authors.lastname: Deng
authors.forename: E W
authors.initials: EW
authors.lastname: Hagley
authors.forename: Qiang
authors.initials: Q
authors.lastname: Cao
authors.forename: Xiaorui
authors.initials: X
authors.lastname: Wang
authors.forename: Xinyu
authors.initials: X
authors.lastname: Luo
authors.forename: Ruquan
authors.initials: R
authors.lastname: Wang
authors.forename: M G
authors.initials: MG
authors.lastname: Payne
authors.forename: Fan
authors.initials: F
authors.lastname: Yang
authors.forename: Xiaoji
authors.initials: X
authors.lastname: Zhou
authors.forename: Xuzong
authors.initials: X
authors.lastname: Chen
authors.forename: Mingsheng
authors.initials: M
authors.lastname: Zhan