A Beliaev Theory Incorporating a Semi-Phenomenological Roton Backflow Effect

Abstract

We have developed a Beliaev theory incorporating a semi-phenomenological roton backflow effect in order to examine the effect of the backflow on the Quantum Evaporation of atoms from the free surface of superfluid 4 He. A theory of Quantum Evaporation based on a real-space Beliaev theory neglecting roton backflow was recently developed by Sobnack et al. [Phys. Rev. B 60, 3465 (1999)], and in this paper we discuss the extension of the theory to include the backflow physics from the Aldrich-Pines polarization potential theory of the 1970's. The calculation of the effect of the backflow on Quantum Evaporation is presented elsewhere.