A Helium-Surface Interaction Potential of Bi2Te3(111) from Ultrahigh-Resolution Spin-Echo Measurements

We have determined an atom-surface interaction potential for the He−Bi2Te3(111) system by analysing ultrahigh resolution measurements of selective adsorption resonances. The experimental measurements were obtained using 3He spin-echo spectrometry. Following an initial free-particle model analysis, we use elastic close-coupling calculations to obtain a three-dimensional potential. The three-dimensional potential is then further refined based on the experimental data set, giving rise to an optimised potential which fully reproduces the experimental data. Based on this analysis, the He−Bi2Te3(111) interaction potential can be described by a corrugated Morse potential with a well depth D=(6.22±0.05) meV, a stiffness κ=(0.92±0.01) 1/Å and a surface electronic corrugation of (9.6±0.2)% of the lattice constant. The improved uncertainties of the atom-surface interaction potential should also enable the use in inelastic close-coupled calculations in order to eventually study the temperature dependence and the line width of selective adsorption resonances.