Phonon thermodynamics versus electron-phonon models

A NUMERICAL RENORMALIZATION GROUP APPROACH FOR AN ELECTRON-PHONON INTERACTION

A finite chain calculation in terms of Hubbard X-operators is explored by setting up a vibronic Harniltonian. The model conveniently transformed into a form so that in the case of strong coupling a numerical renormalization group approach is applicable. To test the technique, a one particle Green function is calculated for the model Harniltonian

Electron -phonon Superconductivity

Phonon dispersion and electron-phonon coupling in MgB2 and AlB2.

We present a first principles investigation of the lattice dynamics and electron-phonon coupling of the superconductor MgB2 and the isostructural AlB2 within the framework of density functional perturbation theory using a mixed-basis pseudopotential method. Complete phonon dispersion curves and Eliashberg functions alpha2F are calculated for both systems. The main differences are related to hig...

Nonlocal screening, electron-phonon coupling, and phonon renormalization in metals.

A method for calculating the phonon self-energy in metals arising from the coupling between phonons and electrons near the Fermi surface is developed. The essence of this scheme is the separation of the inter- and intraband parts of the electron polarizability. The intraband contribution provides extra screenings and is closely related to the electron-phonon coupling and phonon softening in met...

Electron-Phonon Coupling Deduced from Phonon Line Shapes

We investigate the Fano-type line shape of the Ba mode of Y1−xCaxBa2Cu3O6+y films observed in Raman spectra with A1g symmetry. The line shape is described with an extended Fano formula that allows us to obtain the bare phonon parameters and the self-energy effects based on a phenomenological description of the real and imaginary part of the lowenergy electronic response. It turns out that the p...