Excitation spectrum of a3He impurity in superfluid4He

Abstract

We present a variational Monte Carlo calculation of the excitation spectrum of one3He impurity in superfluid4He over the full momentum rang. It includes backflow effects to high order. This is achieved with a shadow wave function in which the phase factors of the excitation are introduced in the subsidiary variables. Energy, effective mass and strength of the single excitation peak of the impurity are computed. Aboveq≃0.5A−1 the effecive mass increases significantly withq in agreement with experiment. No roton like minimum is found and the impurity excitation branch crosses the phonon-roton spectrum atq≃1.6A−1.