We report the first observation of quantized circulation in superfluid . The apparatus consists of a straight vibrating wire immersed in liquid , 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, 0, and +h/2, where h is Planck’s constant and is the mass of the atom. This experiment confirms that superfluid is a Cooper-paired superfluid with a macroscopic quantum wave function.
- Received 19 November 1990
- Published in the issue dated 21 January 1991
© 1991 The American Physical Society