Nonclassical rotational behavior at the vicinity of the lamda point

The rotational property of a quantum liquid at the vicinity of the lamda point Tλ is examined. In a liquid helium 4, shear viscosity shows a slight decrease just above Tλ. We suppose that under the strong influence of Bose statistics, the coherent many-body wave function grows to an intermediate size between a macroscopic and a microscopic size just above Tλ, and suppress the shear viscosity. When it is true, it must have a parallel effect on the rotational properties. Beginning with the bosons without the condensate, we make a perturbation calculation of its susceptibility with respect to the repulsive interaction, and examine how, with decreasing temperature, the growth of the coherent wave function gradually changes the rotational behavior of a liquid. It is shown that the moment of inertia slightly decreases just above Tλ, and that the superfluid density in the mechanical phenomena does not always agree with the thermodynamical superfluid density at the vicinity of Tλ. We compare the result with the experiment by Hess and Fairbank. PACS numbers: 67.40.-w, 67.40.Vs, 67.40.Db, 05.30.Jp Typeset using REVTEX e-mail address: [email protected] 1