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Bubbles with attached quantum vortices in trapped binary Bose-Einstein condensates

Specific topological excitations of energetically stable "core-and-mantle" configurations of trapped two-component immiscible Bose-Einstein condensates are studied numerically within the coupled Gross-Pitaevskii equations. Non-stationary long-lived coherent structures, that consist of several quantum vortex filaments penetrating the "mantle" from outside to inside and vice-versa and demonstrate quite nontrivial dynamics, are observed in simulations for the first time. The ends of filaments can remain attached to the interface between the "mantle" and the "core" if the latter is large enough while the surface tension is not small. The shapes of such "bubbles" are strongly affected by the vortices and sometimes are far from being spherical.