Two-component plasma in a gravitational field
  In this paper we study a model for the sedimentation equilibrium of a charged colloidal suspension: the two-dimensional two-component plasma in a gravitational field which is exactly solvable at a special value of the reduced inverse temperature Gamma=2. The density profiles are computed. The heavy particles accumulate at the bottom of the cointainer. If the container is high enough, an excess of light counterions form a cloud floating at some altitude. 
Gabriel Tellez (Laboratoire de Physique Theorique et Hautes Energies,   Orsay, France)