SINGLE-VORTEX NUCLEATION IN ROTATING SUPERFLUID HE-3-B

Nucleation of vortices in units of one quantum has been observed with c.w. NMR in a rotating cylinder filled with He-3-B. During acceleration a new vortex is created each time the counterflow velocity at the perimeter reaches a critical value v(c)(T, p). The measured v(c) resembles the calculated velocity v(cb)(T, p) of the bulk superflow instability, but is smaller by a factor with power law dependence on the superfluid coherence length. This indicates that a nucleation event takes place whenever the flow exceeds v(cb) locally at the nucleation site and the nucleation barrier vanishes.