Observation of dynamic atom-atom correlation in liquid helium in real space.

ABSTRACT: Liquid ⁴He becomes superfluid and flows without resistance below temperature 2.17?K. Superfluidity has been a subject of intense studies and notable advances were made in elucidating the phenomenon by experiment and theory. Nevertheless, details of the microscopic state, including dynamic atom-atom correlations in the superfluid state, are not fully understood. Here using a technique of neutron dynamic pair-density function (DPDF) analysis we show that ⁴He atoms in the Bose-Einstein condensate have environment significantly different from uncondensed atoms, with the interatomic distance larger than the average by about 10%, whereas the average structure changes little through the superfluid transition. DPDF peak not seen in the snap-shot pair-density function is found at 2.3?Å, and is interpreted in terms of atomic tunnelling. The real space picture of dynamic atom-atom correlations presented here reveal characteristics of atomic dynamics not recognized so far, compelling yet another look at the phenomenon.

SUBMITTER: Dmowski W 

PROVIDER: S-EPMC5418607 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature