Surface and subsurface phonons of Bi(111) measured with helium atom scattering

Helium-surface interaction potential of Sb(111) from scattering experiments and close-coupling calculations

“…Therewith, the experimentally determined surface phonon dispersion will be obtained and a comparison with DFPT results 13 will help to improve theoretical models of the surface dynamics. Based on our results for HAS on Bi(111), 19,20,23 mode-dependent e-ph coupling strengths will be investigated, especially if resonanceenhanced subsurface phonon modes can be detected.…”

“…23 Semimetal surfaces also hold the possibility of detecting electron-hole excitations via HAS due to the fact that electrons on these surfaces are restricted to narrow pockets in the parallel momentum space. 19,20 Furthermore, e-ph scattering processes at the Fermi level are likely to cause Kohn anomalies in the surface phonon dispersion, 19,20,25 an effect which has been observed with HAS for the topological insulator surfaces Bi 2 Se 3 and Bi 2 Te 3 . [26][27][28] In the present work the elastic diffraction peaks of He scattered from Sb(111) are analyzed using the exact closecoupling (CC) method.…”

“…7,9,16 Hence semimetals are particularly interesting for HAS studies since corrugation is necessary for the occurrence of inelastic bound-state resonances which can enhance certain phonon events. 19,20 It was recently shown that inelastic HAS is capable of detecting subsurface phonon modes which are localized in layers beneath the surface in the case of metal and semimetal surfaces. [19][20][21] The depth to which these phonons are observable is determined by the range of the electron-phonon (e-ph) interaction, and inelastic HAS intensities can be used to infer the corresponding e-ph coupling strength.…”

“…19,20 It was recently shown that inelastic HAS is capable of detecting subsurface phonon modes which are localized in layers beneath the surface in the case of metal and semimetal surfaces. [19][20][21] The depth to which these phonons are observable is determined by the range of the electron-phonon (e-ph) interaction, and inelastic HAS intensities can be used to infer the corresponding e-ph coupling strength. 21,22 In a detailed analysis of the intensities on the Bi(111) semimetal surface, a mechanism for the enhancement of inelastic HAS intensities from subsurface optical modes was singled out.…”

Measuring, Interpreting and Translating Electron Quasiparticle - Phonon Interactions on the Surfaces of the Topological Insulators Bismuth Selenide and Bismuth Telluride

“…Helium atom-surface scattering is a high-resolution technique capable of providing valuable information about surface structure and dynamics of metallic and insulating compounds [35][36][37][38]. The technique relies on the production of a monoenergetic helium beam probe that is scattered from solid surfaces, either elastically or inelastically.…”