Path integral Monte Carlo calculation of momentum distribution in solid He-4

Abstract

We perform calculations of the momentum distribution n(k) in solid 4He by means of path integral Monte Carlo methods.We see that, in perfect crystals, n(k)does not depend on temperature T and that is different from the classical Gaussian shape of the Maxwell-Boltzmann distribution, even though these discrepancies decrease when the density of the system increases. In crystals presenting vacancies, we see that for T ≥ 0.75 K, n(k) presents the same behavior as in the perfect crystal, but, at lower T , it presents a peak when k→0.