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oai:recercat.cat:2117/1132822026-01-21T06:28:43Zcom_2072_1033col_2072_452950

00925njm 22002777a 4500 dc Dmowski, Wojtek author Diallo, Souleymane Omar author Lokshin, Konstantin A. author Ehlers, Georg author Ferré Porta, Guillem author Boronat Medico, Jordi author Egami, Takeshi author 2017-05-04 © The Author(s) 2017. 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 atomatom 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 BoseEinstein 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 A, and is interpreted in terms of atomic tunnelling. The real space picture of dynamic atomatom correlations presented here reveal characteristics of atomic dynamics not recognized so far, compelling yet another look at the phenomenon. Postprint (author's final draft) Àrees temàtiques de la UPC::Física Bose-Einstein condensation Bose–Einstein condensates Quantum fluids and solids Condensació de Bose-Einstein Observation of dynamic atom-atom correlation in liquid helium in real space