Abstract
We present a study of the atom–surface interaction potential for the He–Bi2Se3(111) system. Using selective adsorption resonances, we are able to obtain the complete experimental band structure of atoms in the corrugated surface potential of the topological insulator Bi2Se3. He atom scattering spectra show several selective adsorption resonance features that are analyzed, starting with the free-atom approximation and a laterally averaged atom–surface interaction potential. Based on quantum mechanical calculations of the He–surface scattering intensities and resonance processes, we are then considering the three-dimensional atom–surface interaction potential, which is further refined to reproduce the experimental data. Following this analysis, the He–Bi2Se3(111) interaction potential is best represented by a corrugated Morse potential with a well depth of D = (6.54 ± 0.05) meV, a stiffness of κ = (0.58 ± 0.02) Å–1, and a surface electronic corrugation of (5.8 ± 0.2)% of the lattice constant. The experimental data may also be used as a challenging benchmark system to analyze the suitability of several van der Waals approaches: the He–Bi2Se3(111) interaction captures the fundamentals of weak adsorption systems where the binding is governed by long-range electronic correlations.
Highlights
We are going to compare the experimental selective adsorption resonances (SARs) with quantum mechanical scattering calculations to further refine the three-dimensional atom−surface interaction potential
We start with the free-atom approximation and a laterally averaged atom−surface interaction potential, which is further improved and refined based on closecoupled calculations to obtain an accurate three-dimensional atom−surface interaction potential
The He−Bi2Se3(111) potential is best represented by a corrugated Morse potential, which exhibits a well depth of D = (6.54 ± 0.05) meV and a stiffness of κ = (0.58 ± 0.02) Å−1
Summary
The material class of topological insulators (TIs) has lately received broad attention[1−6] due to their protected metallic surface states and the insulating bulk electronic structure.[7,8] An archetypal TI and one of the most studied examples is the here presented Bi2Se3.9,10 Topological surfaces show modifications of their electronic structure upon adsorption of atoms and molecules.[11−14] the interaction of TI surfaces with their environment, that is, atom−surface interaction potentials are barely investigated by the experiment despite the fact that topology can have implications far beyond electronic transport properties and topological materials, provides a perfect platform for studying phenomena such as heterogeneous catalysis or sensing applications.[15,16]. The atom−surface interaction potential is a necessary ingredient for quantum mechanical calculations of elastic scattering intensities,[35−37] allowing for a comparison with experimentally observed He diffraction peak intensities In this context, the influence of vdW forces in atom−surface scattering calculations of noble gases has recently been studied,[35,38] and the experimental diffraction intensities may even be used as a benchmark to test the performance of different vdW-corrected DFT approaches.[39]. The comparison with diffraction intensities merely considers a small number of diffraction channels, which are accessible in the experiment, and a comparison of quantum mechanical scattering calculations with SARs provides an even more rigorous test in terms of the sought atom−surface interaction potential. K) allow us to obtain further details of the SARs and the atom−surface interaction potential (see Refinement of the Interaction Potential)
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