Electron-phonon coupling and surface Debye temperature of Bi2 Te3 (111) from helium atom scattering

Abstract

We have studied the topological insulator Bi2Te3(111) by means of helium atom scattering. The average electron-phonon coupling λ of Bi2Te3(111) is determined by adapting a recently developed quantum-theoretical derivation of the helium scattering probabilities to the case of degenerate semiconductors. Based on the Debye-Waller attenuation of the elastic diffraction peaks of Bi2Te3(111), measured at surface temperatures between 110 and 355K, we find λ to be in the range of 0.04-0.11. This method allows us to extract a correctly averaged λ and to address the discrepancy between previous studies. The relatively modest value of λ is not surprising even though some individual phonons may provide a larger electron-phonon interaction. Furthermore, the surface Debye temperature of Bi2Te3(111) is determined as ΘD=(81±6)K. The electronic surface corrugation was analyzed based on close-coupling calculations. By using a corrugated Morse potential a peak-to-peak corrugation of 9% of the lattice constant is obtained.