Two stages in the evolution of binary alkali Bose-Einstein condensate mixtures towards phase segregation

The quantum analogy of the usual spinodal decomposition is explored for the recently achieved binary alkali Bose-Einstein condensates mixture. We conc lude that an analogy is possible within the formulation of coupled nonlinea r Schrodinger equations, and find that the quantum spinodal decomposition c onsists of two stages. The non-equilibrium stage I is dominated by the fast est growth mode, associated with a characteristic length. Expressions for b oth time and length scales in stage I are obtained. Stage II is a relaxatio n process of approaching equilibrium, dominated by the slowest mode. We pro pose that for this state the slow evolution towards the phase segregation i s due to the Josephson effect between different domains of the same condens ate, and its time scale is estimated.