A Comparison of the Properties of Superconductors and Superfluid Helium
This chapter aims to show that there is a remarkably close similarity between superfluid helium and a superconductor in very many essential properties. An important is that for a complete understanding of superfluidity we ought really to study both systems. Superfluid helium is usually an extremely good conductor of heat. The mechanism of heat conduction is, however, quite different from that obtaining in an ordinary material, and it consists in a counterflow of the two fluids, with no net mass flow, the superfluid moving against the temperature gradient and the normal fluid with it. A real superconductor differs from the Fermi superfluid discussed in three important respects. First, the particles in the superconductor are electrically charged, and move in a charge-neutralizing positive ion background. Second, the electrons in the superconductor suffer scattering from imperfections in the positive ion lattice. Third, the electron–electron interaction responsible for superconductivity is not a simple delta function but is instead a complicated phonon-mediated process.