Use of surface-wave spectroscopy to characterize tilt modes of a vortex ina Bose-Einstein condensate

A vortex in a condensate in a nonspherical trapping potential will in gener al experience a torque. The torque will induce tilting of the direction of the vortex axis. We observe this behavior experimentally and show that by a pplying small distortions to the trapping potential, we can control the til ting behavior. By suppressing vortex tilt, we have been able to hold the vo rtex axis along the line of sight for up to 15 sec. Alternatively, we can i nduce a 180 degrees tilt, effectively reversing the charge on the vortex as observed in the lab frame. We characterize the vortex nondestructively wit h a surface-wave spectroscopic technique.