Evidence of an Internally Generated Optical-Dipole Potential in   Matter-Wave Superradiance
  We present the first experimental evidence supporting the postulation that an optical-dipole potential in a condensate undergoing superradiant scattering modifies the structure factor of the system and significantly impacts the scattering. Several consequences of this new detuning-dependent mechanism are discussed and verified experimentally. Our experiments indicate that whenever the generation and propagation growth of a new field are significant, the dynamic response of the condensate can have a profound impact on the scattering process. 
Xinyu Lou, L. Deng, E.W. Hagley, Kuiyi Gao, Xiaorui Wang, and Ruquan   Wang
quant-ph cond-mat.quant-gas