  The rotational properties of a mixture of two distinguishable Bose gases that
are confined in a ring potential provide novel physical effects that we
demonstrate in this study. Persistent currents are shown to be stable for a
range of the population imbalance between the two components at low angular
momentum. At higher values of the angular momentum, even small admixtures of a
second species of atoms make the persistent currents highly fragile.

Quantum Gases