LAUSR

When the spectrum of magnetic excitations of a quantum mixture is much softer than the density spectrum, the system becomes effectively incompressible and can host magnetic defects. These are characterized by the presence of a topological defect in one of the two species and by a local modification of the density in the second one, the total density being practically unaffected. For miscible mixtures interacting with equal intraspecies coupling constants, the width of these magnetic defects is fixed by the difference $\ensuremath{\delta}g$ between the intraspecies and interspecies coupling constants and becomes increasingly larger as one approaches the demixing transition at $\ensuremath{\delta}g=0$. When the density of the filling component decreases, the incompressibility condition breaks down, and we predict the existence of a critical filling, below which all the atoms of the minority component remain bound in the core of the topological defect. Applications to the sodium atomic spin species $|F=1,{m}_{F}=\ifmmode\pm\else\textpm\fi{}1\ensuremath{\rangle}$ in both uniform and harmonically trapped configurations are considered, and a protocol to produce experimentally these defects is discussed. The case of binary mixtures interacting with unequal intraspecies forces and experiencing buoyancy is also addressed.