  Clouds of cold neutral atoms driven by a coherent light beam in a ring cavity
exhibit self-structured states transversely with respect to the beam axis due
to optomechanical forces and the back action of the atomic structures on the
beam. Below the instability threshold for extended hexagonal structures,
localized soliton-like excitations can be stable. These constitute peaks or
holes of atom density, depending on the linear susceptibility of the cloud.
Complex rotating and spiralling motion of coupled atom-light solitons, and
hence atomic transport, can be achieved via phase gradients in the input field
profile. We also discuss the stability of rotating soliton chains in view of
soliton-soliton interactions. The investigations are performed in a cavity
scheme but expected to apply to other longitudinally pumped schemes with
diffractive coupling.
