Nonlinear Electron-phonon Coupling Research Articles

Common aspects of ferroelectricity and high-temperature superconductivity

Abstract The lattice dynamics of high-temperature superconducting oxides are investigated within an extended version of the polarizability model of displacive type ferroelectrics. The local non-linear electron-phonon coupling together with an electronic instability are suggested to play the driving mechanism for electron pairing in superconductors. The transformation of the classical Hamiltonian to an extended Peierls-Hubbard type model admits the investigation of parameter regimes where pairing of electrons (holes) occurs.

Nonlinear lattice-dynamical theory of mixed-valence compounds

by M. Cardona The unusual temperature dependence of anomalies of phonon dispersion curves in Sm 0.75Y 0.25S is interpreted by means of nonlinear electron-phonon coupling. The γ 1-symmetry coupling is attributed primarily to the fluctuations of Sm electrons between f and d states. In as much as the anomalies in the phonon dispersion curves are seen only in the longitudinal modes in the Λ direction, they can be treated exactly in a one-dimensional projection.

Optical properties of Cu+ ions in RbMgF3 crystals.

The absorption, emission, and excitation spectra, as well as the lifetimes, have been measured for Cu/sup +/ ions substituting for Rb/sup +/ ions in two different sites in RbMgF/sub 3/ crystals. The (3d)/sup 10/..-->..(3d)/sup 9/(4s) absorption transitions occur in the ultraviolet with optical emission at 450 and 575 nm. The two emission bands have been attributed to Cu/sup +/ ions occupying two different sites. From the results of polarized excitation experiments, the electronic structure of the crystal-field-split levels of the (3d)/sup 9/(4s) configuration of Cu/sup +/ ions at the two sites can be determined. The 575-nm luminescence is quenched above 300 K. This quenching is ascribed to nonradiative multiphonon emission which is enhanced significantly by strong nonlinear electron-phonon coupling.