Observation of the optical and acoustic electron-phonon coupling in Sc, Y and Lu dihydrides and dideuterides by electrical resistivity

The electrical resistivities of Sc, Y and Lu and of their dihydrides and dideuterides have been measured in the temperature range 4.5-300K. They reveal, for the first time in these systems, a contribution from optical phonons which the authors analyse in the harmonic approximation. The coupling to these optical H(D) phonons is found to be much weaker than the corresponding coupling to the acoustic or host phonons. This latter coupling is also weaker in the hydrides than in the hydrogen-free metals. All the observed features are in reasonable agreement with the known facts about the electronic structure of the metals. The absence of superconductivity in the hydrides is also understood in this scheme.