Partial delocalization of two-component condensates in optical lattices

We study management of localized modes in two-component (spinor) Bose-Einstein condensates embedded in optical lattices by changing interspecies interactions. By numerical integration of the coupled Gross-Pitaevskii equations, we find three different regimes of the delocalizing transition: i) the partial delocalization when the chemical potential of one of the components collapses with a gap edge and the respective component transforms into a Bloch state, while the other component remains localized; ii) the partial delocalization as consequence of instability of one of the components; and iii) the situation where the vector soliton reaches limits of the existence domain. It is shown that there exists a critical value for interspecies scattering length, below which solutions can be manipulated and above which one of the components is irreversibly destroyed.