Surface properties of 1T-TaS(2) and contrasting its electron-phonon coupling with TlBiTe(2) from helium atom scattering

We present a detailed helium atom scattering study of the charge-density wave (CDW) system and transition metal dichalcogenide 1T-TaS(2). In terms of energy dissipation, we determine the electron-phonon (e-ph) coupling, a quantity that is at the heart of conventional superconductivity and may even “drive” phase transitions such as CDWs. The e-ph coupling of TaS(2) in the commensurate CDW phase (λ = 0.59 ± 0.12) is compared with measurements of the topo-logical insulator TlBiTe(2) (λ = 0.09 ± 0.01). Furthermore, by means of elastic He diffraction and resonance/interference effects in He scattering, the thermal expansion of the surface lattice, the surface step height, and the three-dimensional atom-surface interaction potential are determined including the electronic corrugation of 1T-TaS(2). The linear thermal expansion coefficient is similar to that of other transition-metal dichalcogenides. The He−TaS(2) interaction is best described by a corrugated Morse potential with a relatively large well depth and supports a large number of bound states, comparable to the surface of Bi(2)Se(3), and the surface electronic corrugation of 1T-TaS(2) is similar to the ones found for semimetal surfaces.