Dynamical Structure Factor and Spin-Density Separation for a   Weakly-Interacting Two-Component Bose Gas
  We show that spin-density separation in a Bose gas is not restricted to 1D but also occurs in higher dimension. The ratio ($\alpha$) of the intra-species atom-atom interaction strength to the inter-species interaction strength, strongly influences the dynamics of spin-density separation and the elementary excitations. The density wave is phonon-like for all values of $\alpha$. For $\alpha<1$, spin wave is also phonon-like. The spin waves have a quadratic dispersion in the $\alpha=1$ coupling regime, while in the phase separated regime ($\alpha>1$) the spin waves are found to be damped. The dynamical structure factor (DSF) reveals two distinct peaks corresponding to the density and spin waves for $\alpha \le 1$. For $\alpha > 1$ there is only one DSF peak corresponding to the density wave. 
M.-C. Chung and A. B. Bhattacherjee