  In this paper we analyze the possibility of persistent currents of a
two-species bosonic mixture in the one-dimensional ring geometry. We extend the
arguments used by Bloch to obtain a criterion for the stability of persistent
currents for the two-species system. If the mass ratio of the two species is a
rational number, persistent currents can be stable at multiples of a certain
total angular momenta. We show that the Bloch criterion can also be viewed as a
Landau criterion involving the elementary excitations of the system. Our
analysis reveals that persistent currents at higher angular momenta are more
stable for the two-species system than previously thought.
