arXiv:cond-mat/9708226 · Physical Review Letters
Critical Velocity of Vortex Nucleation in Rotating Superfluid 3 He- A
V. M. H. Ruutu, Juha Kopu, M. Krusius, Ülo Parts, Bernard Plaçais, E. V. Thuneberg, W. Xu
Abstract
We have measured the critical velocity ${\ensuremath{\upsilon}}_{\mathrm{c}}$ at which ${}^{3}\mathrm{He}\ensuremath{-}\mathrm{A}$ in a rotating cylinder becomes unstable against the formation of quantized vortex lines with continuous (singularity-free) core structure. We find that ${\ensuremath{\upsilon}}_{\mathrm{c}}$ is distributed between a maximum and a minimum limit, which we ascribe to a dependence on the texture of the orbital angular momentun axis $\stackrel{^}{\mathbf{l}}(\mathbf{r})$ in the cylinder. Slow cooldown through ${T}_{\mathrm{c}}$ in rotation yields $\stackrel{^}{\mathbf{l}}(\mathbf{r})$ textures for which the measured ${\ensuremath{\upsilon}}_{\mathrm{c}}$'s are in good agreement with the calculated instability of the expected $\stackrel{^}{\mathbf{l}}$ texture.