Vortex core states in superfluid Fermi-Fermi mixtures with unequal masses

We analyze the vortex core states of two-species (mass imbalanced) superfluid fermion mixtures as a function of two-body binding energy in two dimensions. In particular we solve the Bogoliubov-de Gennes equations for a population balanced mixture of ${}^6$Li and ${}^{40}$K atoms at zero temperature. We find that the vortex core is mostly occupied by the light-mass (${}^6$Li) fermions and that the core density of the heavy-mass (${}^{40}$K) fermions is highly depleted. This is in contrast with the one-species (mass balanced) mixtures with balanced populations where an equal amount of density depletion is found at the vortex core for both pseudospin components.