paper

Electron-phonon coupling and phonon self-energy in MgB $_{2}$ : do we really understand MgB $_{2}$ Raman spectra ?

arXiv:cond-mat/0406072 · doi:10.1103/PhysRevB.71.064501

Abstract

We consider a model Hamiltonian fitted on the ab-initio band structure to describe the electron-phonon coupling between the electronic $I ¨ -$ bands and the phonon E $_{2 g}$ mode in MgB $_{2}$ . The model allows for analytical calculations and numerical treatments using very large k-point grids. We calculate the phonon self-energy of the E $_{2 g}$ mode along two high symmetry directions in the Brillouin zone. We demonstrate that the contribution of the $I ¨ $ bands to the Raman linewidth of the E $_{2 g}$ mode via the electron-phonon coupling is zero. As a consequence the large resonance seen in Raman experiments cannot be interpreted as originated from the $E_{2 g}$ mode at $I^$ . We examine in details the effects of Fermi surface singularities in the phonon spectrum and linewidth and we determine the magnitude of finite temperature effects in the the phonon self-energy. From our findings we suggest several possible effects which might be responsible for the MgB $_{2}$ Raman spectra.

10 pages, 9 figures

Electron-phonon coupling and phonon self-energy in MgB2​: do we really understand MgB2​ Raman spectra ?

Abstract

Electron-phonon coupling and phonon self-energy in MgB $_{2}$ : do we really understand MgB $_{2}$ Raman spectra ?