LOW-TEMPERATURE PROPERTIES OF LIQUID-HE-3

Reviews the theory describing the low-temperature properties of liquid 3He, and in particular the superfluid A and B phases. It emphasises basic physical concepts rather than detailed quantitative calculations. Advanced formal techniques such as Green functions are avoided. The low-temperature properties of liquid 3He are explained in terms of a gas of elementary excitations or quasiparticles, as proposed by Landau (1956). The superfluid phases are described by a straightforward generalisation of the concept of quasiparticle pair correlations introduced by Bardeen et al. (1957) in the context of superconductivity, with the exception of very few qualitative properties, such as the stability of model states (strong coupling effects), or the behaviour very close to the transition (pair fluctuation effects). The identification of 3He-A and 3He-B with the p-wave spin triplet pairing model states introduced by Anderson and Morel (1961) and Anderson and Brinkman (1973), and by Balian and Werthamer (1963), respectively, leads to good agreement with the bulk of experimental observations.