Possible vortex production by a vibrating wire in superfluid He–B

We observe spectacular features on the force–velocity characteristic of a vibrating wire resonator in superfluid ³He–B at ultralow temperatures. There are both plateaux and discontinuities in the characteristic. The plateaux seem to have two separate critical velocities where firstly some ‘event’ occurs, which causes the wire to lose energy and slow down, followed by a second critical velocity where the ‘event’ decouples. The shape of the pulses so created depends on the precise position on the particular plateau. At the low-velocity end of the plateau, the pulses show a sudden decrease in velocity followed by a gradual growth, whereas at the high-velocity end the pulses consist of a sudden increase in velocity followed by a gradual decrease. Eventually, the pulsing ceases indicating a saturation effect. We speculate that these events are due to vortex creation and annihilation/separation.