  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.
