Solid 4He in Narrow Porous Media

Abstract

We give a variational Monte Carlo description at T = 0 K of 4He filling a porous glass within the shadow wave function technique. The confining media is modeled by a smooth cylindrical pore, and we have considered two different pore radii: R = 13 A and R = 22.5 A. The radial density profiles show a strong layering of the 4He atoms. In the R = 13 A pore, as the density is increased, solidification takes place layer by layer, starting from the pore wall, and the radius is too small to allow a bulk‐like solid to nucleate in the small liquid region at the center of the pore. For the R = 22.5 A pore we find an hcp lattice accommodated in the central region surrounded by four layers which turn out to be solid at the density of the computation. Computing the one‐body density matrix (in the R = 13 A case) we are able to estimate the Bose‐Einstein condensate fraction, which is still non‐zero even when the whole system is in the solid phase.