Bose-Einstein Condensate in Solid Helium
Abstract
We present neutron scattering measurements of the atomic momentum distribution, n(k), in solid helium under a pressure p = 41 bars and at temperatures between 80 mK and 500 mK. The aim is to determine whether there is Bose-Einstein condensation (BEC) below the critical temperature, Tc = 200 mK where a superfluid density has been observed. Assuming BEC appears as a macroscopic occupation of the k = 0 state below Tc, we find a condensate fraction of n0 = (-0.10 1.20)% at T = 80 mK and n0 = (0.080.78)% at T = 120 mK, consistent with zero. The shape of n(k) also does not change on crossing Tc within measurement precision.
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