Approximate wave functions of the form G(n(k)), where G is a correlation operator that contains two-body, three-body, and momentum-dependent correlations, and (n(k)) is a noninteracting-Bose-gas wave function with occupation numbers n(k), are used to calculate the energies of excited states of liquid He4. The energy expectation values are calculated by generalizing the Fermi hypernetted-chain methods. The single-quasiparticle excitation spectrum provides stringent tests for the correlation operator G. The calculated phonon, maxon spectra are not in good agreement with the experimental results presumably because of the truncations in the large-distance behavior of the two-body correlations in the G. The results obtained for the roton energies are in good agreement with the experiments over the range of liquid-He4 density.
ASJC Scopus subject areas
- Condensed Matter Physics