Classical and quantum description of the atomic motion in superradiant light scattering from Bose-Einstein condensates

A theory of coherent light scattering from an elongated Bose-Einstein condensate exposed to an off-resonant laser beam is presented. The model describes the emission of two superradiant pulses along the sample's major axis simultaneous with the formation of a bidimensional atomic grating inside the sample, as was observed in a recent MIT experiment [Inouye, S. et al., 1999, Science, 285, 571]. We predictions of the semiclassical model, in which the atomic motion is treated classically, are compared with these of the quantum model, obtained including the quantum mechanical description of the atomic motion. In the quantum limit the superradiant regime becomes a sequential process, in which during each collective scattering atoms emit a it hyperbolic secant pulse and populate an adjacent momentum state.