Quantum reflection, evaporation, and transport currents at ⁴He surfaces

In this work, we study transport currents in excited states. This requires the calculation of particle currents 〈n|ĵ|n〉 to second order in the excitation amplitudes. For that purpose, we take a well-tested microscopic theory of inhomogeneous quantum liquids and extend it to find the mass currents created when atoms scatter off a surface or when excitations evaporate atoms. This is the first theoretical study of transport phenomena in a quantum liquid based on a quantitative microscopic theory.