We present a theory describing the lambda transition and the Bose-Einstein condensation (BEC) in a liquid 4He based on the diatomic quasiparticle concept. It is shown that in liquid 4He for the temperature region 1 K ≤ T ≤ Tλ the diatomic quasiparticles macroscopically populate the ground state which leads to BEC in liquid 4He. The approach yields the lambda transition temperature as Tλ = 2.16 K which is in excellent agreement with the experimental lambda temperature Tλ = 2.17 K. The concept of diatomic quasiparticles also leads to superfluid and BEC fractions which are in a good agreement with the experimental data and Monte Carlo simulations.
We present a theory describing the lambda transition and the Bose-Einstein condensation (BEC) in a liquid 4He based on the diatomic quasiparticle concept. It is shown that in liquid 4He for the temperature region 1 K ≤ T ≤ Tλ the diatomic quasiparticles macroscopically populate the ground state which leads to BEC in liquid 4He. The approach yields the lambda transition temperature as Tλ = 2.16 K which is in excellent agreement with the experimental lambda temperature Tλ = 2.17 K. The concept of diatomic quasiparticles also leads to superfluid and BEC fractions which are in a good agreement with the experimental data and Monte Carlo simulations.