UC Davis
Rena Zieve Group

Superfluid Helium Vortices

Understanding vortex motion is important for studies of neutron stars, superconductors, and turbulence in classical fluids. We have an unusual technique for observing the motion of a single superfluid vortex through its effects on a vibrating wire. Our system allows detailed comparison with computer simulations and exploration of various influences on the vortex. Our present goal is understanding the mechanisms by which a vortex interacts with the walls of the container.

Our experimental setup consists of a brass cylinder filled with liquid helium. A fine superconducting wire is stretched along the cell, displaced from the cylinder's axis. If the wire serves as the core of a superfluid vortex, its vibrational normal modes change. A vortex can also be partially attached, with its core running along a portion of the wire, then traversing the fluid as a free vortex. In this case, any motion of the free portion gets reflected in motion of the attachment point, which we observe.

We can explore features of the vortex behavior such as how it pins to bumps on the container wall or works its way free, and how its motion dissipates energy. We complement our measurements with computer simulations of superfluid vortices. The graph below compares physical data as a vortex pins (top curve) with a computer simulation for pinning in the same geometry (bottom curve); the computational results confirm our interpretation of the data.

Here are elementary discussions of superfluid helium, superfluid vortices and our helium measurements.

Some recent papers:

``Energy loss from a moving vortex in superfluid helium," R.J. Zieve, C.M. Frei, and D.L. Wolfson, Phys. Rev. B 86, 174504 (2012); also at arXiv:1209.1410

``Energy loss from reconnection with a vortex mesh," I.H. Neumann and R.J. Zieve, Phys. Rev. B 81, 174515 (2010); also at arXiv:1010.0365