Accurate description of the van der Waals interaction of an electron-positron pair with the surface of a topological insulator

13th International Workshop on Slow Positron Beam Techniques and Applications

Saniz, R.^1 ; Vercauteren, S.^1 ; Lamoen, D.^1 ; Partoens, B.^1 ; Barbiellini, B.^2

CMT and EMAT, Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium^1

Physics Department, Northeastern University, Boston, MA 02115, United States^2

关键词: Electron-positron pairs;    Interaction potentials;    Parameter-free methods;    Positron spectroscopy;    Surface electron;    Topological insulators;    Van der Waals interaction;    Van Der Waals interactions;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/505/1/012002/pdf
DOI  :  10.1088/1742-6596/505/1/012002

来源: IOP

【 摘 要 】

Positrons can be trapped in localized states at the surface of a material, and thus quite selectively interact with core or valence surface electrons. Hence, advanced surface positron spectroscopy techniques can present the ideal tools to study a topological insulator, where surface states play a fundamental role. We analyze the problem of a positron at a TI surface, assuming that it is a weakly physisorbed positronium (Ps) atom. To determine if the surface of interest in a material can sustain such a physisorption, an accurate description of the underlying van der Waals (vdW) interaction is essential. We have developed a first-principles parameter-free method, based on the density functional theory, to extract key parameters determining the vdW interaction potential between a Ps atom and the surface of a given material. The method has been successfully applied to quartz and preliminary results on Bi2Te2Se indicate the existence of a positron surface state. We discuss the robustness of our predictions versus the most relevant approximations involved in our approach.