Bose-Einstein condensation in solid helium

We report new measurements of the Bose-Einstein condensate fraction in solid helium. The goal is to reveal whether there is BEC associated with the superfluid fractions that have been observed in solid helium [1,2]. The condensate fraction, n$_0$, is obtained from neutron scattering measurements of the momentum distribution, n(k), of the atoms in the solid. We use commercial grade helium ($^3$He concentration of 0.3 $\%$) where the T$_c$ for superflow is T$_c$ = 200 mK and have measured the n(k) at 3 temperatures, 500 mK, 150 mK and 65 mK. We use a sample cell that has a large surface to volume ratio (S/V) = 40 cm$^{-1}$ where large superfluid fractions have recently been reported[2]. We use a large sample volume (100 cm$^3$) and high instrument resolution to improve precision beyond that of previous measurements [3]. No clear sign of BEC has been observed but the data is being analyzed so that specific values of n$_0$ can be reported. [1] E. Kim and M.H.W. Chan. Science, 305:1941 (2004); Nature, 427:225, 2004. [2]A. S. C. Rittner, and J. D. Reppy, Phys. Rev. Lett., 98:175302, 2007. [3] Diallo et al. Phys. Rev Lett. 98, 205301 (2007).