Hysteresis and persistent currents in a rotating Bose-Einstein condensate with anharmonic confinement

We examine a Bose-Einstein condensate of atoms that rotates in a quadratic-plus-quartic potential. It is shown that states of different circulation can be metastable. As a result, we demonstrate that the gas can exhibit hysteresis as the angular frequency of rotation of the trap is varied. The simplicity of the picture that emerges for small coupling strengths suggests that this system may be attractive for studies of phase transitions.