Transition in Wave Behavior on a Superfluid Vortex at Large Excitation Amplitude

We study a single quantized vortex stretched between a wire and the wall of a cylindrical container. The wire serves both as a probe and as a means of exciting the system. Vibrating the wire creates oscillations along the vortex. One consequence of these oscillations is that the spot where the vortex joins the wire moves. This in turn changes the normal modes of the wire's vibration, which lets us detect the vortex location. We find a qualitative change in behavior at sufficiently large excitation. Below the crossover, clear vortex waves are induced, with amplitude near the expected threshold for instability. As the excitation increases, the signal becomes much less regular. Higher-frequency oscillations appear, as well as a slow feature that may indicate recurrence. The vortex appears to undergo significant length changes during the process.