Temperature dependence of the condensate fraction in superfluid 4He

A temperature-dependent expression for the condensate fraction n0 for He II based on a model Hamiltonian for superfluids is presented. This gives roughly the same magnitude for n0 as is observed. The model also suggests the following behavior as T→0 for the roton effective mass μ/sub r/(T)=μ/sub r/(0)[1-(m/sub He//24h3cn)(k/sub B/T)2] and the roton minimum energy Δ(T)=Δ(0)[1-(m/sub He//24h3cn)(k/sub B/T)2]