Electron-phonon coupling in superconducting 1T-PdTe2

We have determined the electron-phonon interaction in type II Dirac semimetallic 1T-PdTe2 by means of helium atom scattering. While 1T-PdTe2 is isostructural with 1T-PtTe2, only the former is superconductor. The difference can be traced to the substantially larger value of the electron-phonon coupling in 1T-PdTe2, lambda = 0.58, obtained from the Debye-Waller attenuation of the He specular peak. With this value and the surface Debye temperature, Theta(D) = 106.2 K, we have figured out the superconducting critical temperature, T-c = 1.83 K given by the BCS theory, which is in good agreement with T-c = (1.95 +/- 0.03) K obtained with low-temperature scanning tunneling microscopy. The value of the effective mass related to Theta(D) indicates that the large electron-phonon coupling in 1T-PdTe2 is due to coupling, not only with the zone-center optical mode O-2 at 9.2 meV, as proposed in a recent theoretical study, but also with the zone-boundary acoustic mode LA. Our results suggest that the topological states of a Dirac cone play a negligible role on the onset of superconductivity.