2005/03/17 by D. E. Galli, M. Rossi, L. Reatto
Physics and Astronomy · #Atomic and Subatomic Physics Research #Cold Atom Physics and Bose-Einstein Condensates #Quantum, superfluid, helium dynamics #cond-mat.stat-mech
paper · pdf · doi:10.1103/physrevb.71.140506
4 pages, 3 figures, accepted for publication as a Rapid Communication in Physical Review B
arxiv created 2005/03/17 · openalex publication_date 2005/04/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We have computed the one-body density matrix \ensuremathρ1 in solid 4He at T=0\phantom\rule0.3em0exK using the shadow wave-function (SWF) variational technique. The accuracy of the SWF has been tested with an exact projector method. We find that off-diagonal long-range order is present in \ensuremathρ1 for a perfect hcp and bcc solid 4He for a range of densities above the melting one, at least up to 54 bars. This is first microscopic indication that Bose Einstein condensation (BEC) is present in perfect solid 4He. At melting, the condensate fraction in the hcp solid is 5\ifmmode×\else\texttimes\fi10^\ensuremath-6 and it decreases by increasing the density. The key process giving rise to BEC is the formation of vacancy interstitial pairs. We also present values for Leggett's upper bound on the superfluid fraction deduced from the exact local density.