VORTEX SHEET IN SUPERFLUID HE-3-A

The vortex sheet (VS) is the most unexpected discovery in rotating sup erfluids during the last ten years. Usually superfluids respond to rot ation by creating an array of vortex lines, which are parallel to the rotation axis, and tile circulation around them is quantized. In the V S the vorticity is located on a 2 dimensional sheet that folds to equi distant layers in a rotating container. The VS is one out of five stab le vortex structures in He-3-A. The stability of the VS in He-3-A aris es from a special structure, which consists of a nonsingular vorticity bound to a topologically stable domain wall. The vortex sheet forms t he equilibrium state of He-3-A at rotation velocities larger than simi lar to 3 rad/s, but it is also created as metastable state at lower ve locities. Experimentally the vortex sheet is distinguished from its NM R response.