Experimental determination of surface thermal expansion and electron-phonon coupling constant of 1T-PtTe₂

We report an extensive structural characterization of the surface of 1T-PtTe₂ crystals by means of helium atom scattering (HAS) and ultra-high resolution scanning tunnelling microscopy (STM). HAS reveals that this bi-dimensional surface presents a large structural corrugation (∼0.33 Å) in ΓM̄ direction. The surface lattice constant of PtTe₂ derived from the positions of the helium diffraction peaks up to fifth order was found to be a = (3.96 ± 0.05) Å, in agreement with STM and x-ray diffraction measurements. This value remains unchanged in the temperature range between 90 and 580 K. These findings suggest that 1T-PtTe₂ behaves similarly to graphene on a weakly-interacting substrate, for which the surface thermal expansion coefficient is zero within experimental error. The electron-phonon coupling constant λ has been determined by recording the thermal attenuation of the elastic diffraction peaks of PtTe₂. Based on a recently developed quantum theoretical method adapted to layered degenerate semiconductors we find that λ lies between 0.38-0.42.