Spatial separation of rotating binary Bose-Einstein condensates by tuning the dipolar interactions

Abstract

We are pointing out relevant anisotropic effects, related to spatial separation, miscibility and mass-symmetry, due to dipole-dipole interactions in rotating binary dipolar Bose-Einstein condensates, by considering symmetric ($^{164}$Dy-$^{162}$Dy) and asymmetric ($^{168}$Er-$^{164}$Dy, $^{164}$Dy-$^{87}$Rb) dipolar mixtures. The binary mixtures are kept in strong pancake-shaped trap, modeled by an effective two-dimensional coupled Gross-Pitaevskii equation. The anisotropy of the dipolar interactions, on miscibility and vortex-lattice structures, is studied by tuning the polarization angle of the dipoles $\varphi$, which can enhance the attractive part of the dipole-dipole interaction (DDI) for both inter- and intra-species. Within this procedure of changing to attractive the DDI, a clear spatial separation is verified in the densities at some critical polarization angle. The spatial separations, being angular for symmetric mixtures and radial for asymmetric ones, are verified for repulsive contact interactions when the inter- to intra-species ratio $\delta$ is larger than one, implying the system is less miscible. The corresponding result for the critical polarization angle as a function of $\delta$ is shown in the particular dipolar symmetric case. A striking outcome of the present study is the observed sensibility of the vortex-pattern binary distributions due to the mass-asymmetry. This is exemplified by the symmetric dipolar mixture, where the two isotopes are of the same species.