Microscopic Theory of Superfluid Helium

S. Stringari, F. Dalfovo, M. Guilleumas +2 more

Franklin Pollock

Juha Kopu

K.H. Bennemann, John B. Ketterson

This chapter covers some of the basics of superfluidity. It discusses Bose–Einstein condensation in an ideal gas; the Bogoliubov transformation; superfluid helium II; microscopic interpretation of the Bose order parameter; phenomenological theories of superconductivity; the Bardeen–Cooper–Schrieffer (BCS) theory of superconductivity; the first unusual superfluid, 3He; and recent developments in superfluidity.

L. E. Reichl

T. Kebukawa, Shosuke Sasaki

A microscopic theory of the ac Josephson effect in superfluid helium is proposed on the basis of the Heisenberg equation of the dressed-boson operators. The equation is solved exactly. The interference of the two eigen-oscillations in the exact solution produces the Josephson oscillation. It is verified that the oscillation occurs even when the quantum fluctuation of the relative phase is infinitely large. On the basis of these results, we propose an experiment to detect the tunnelling effect of the dressed-bosons. The formulation of this paper can be applied to the Josephson effect in superconductor.