Mixing, demixing, and structure formation in a binary dipolar Bose-Einstein condensate

We study static properties of disk-shaped binary dipolar Bose-Einstein condensates of $^{168}$Er-$^{164}$Dy and $^{52}$Cr-$^{164}$Dy mixtures under the action of inter- and intra-species contact and dipolar interactions and demonstrate the effect of dipolar interaction using the mean-field approach. Throughout this study we use realistic values of inter- and intra-species dipolar interactions and the intra-species scattering lengths and consider the inter-species scattering length as a parameter. The stability of the binary mixture is illustrated through phase plots involving number of atoms of the species. The binary system always becomes unstable as the number of atoms increases beyond a certain limit. As the inter-species scattering length increases corresponding to more repulsion, an overlapping mixed state of the two species changes to a separated demixed configuration. During transition from a mixed to a demixed configuration as the inter-species scattering length is increased for parameters just below the stability line, the binary condensate shows special structures in density in the form of red-blood-cell-like biconcave and Saturn-ring-like shapes, which are direct manifestations of dipolar interaction.