Macroscopic quantum tunneling of vortices in He II

Abstract

Experimental evidence is presented showing that the creation of vortices in He II involves macroscopic quantum tunneling through, or thermal activation over, a potential-energy barrier ε. The investigations, based on measurements of the rate at which negative ions create vortex rings in the isotopically pure superfluid within the temperature range 50<T<500 mK, have yielded a barrier height of ε/$k_{\mathrm{B}=3.1\mathrm{}\pm 0.1}$ K, in excellent agreement with the theoretical value predicted by Muirhead, Vinen, and Donnelly.