Observation of quantized circulation in superfluidB3

Abstract

We report the first observation of quantized circulation in superfluid ${}_{}{}^3{}_{}{}^{}\mathit{B}$. The apparatus consists of a straight vibrating wire immersed in liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, which is cooled by a rotating nuclear demagnetization cryostat. The experiment is carried out at about 250 μK. The superfluid at this temperature is in the ballistic quasiparticle regime. Circulation around the wire is found to be stable only when it takes on the values -h/2${\mathit{m}}_3$, 0, and +h/2${\mathit{m}}_3$, where h is Planck’s constant and ${\mathit{m}}_3$ is the mass of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ atom. This experiment confirms that superfluid ${}_{}{}^3{}_{}{}^{}\mathit{B}$ is a Cooper-paired superfluid with a macroscopic quantum wave function.