Electronic dispersion anomalies in iron pnictide superconductors.

Recently, experimental studies of the spin excitation spectrum revealed a strong temperature dependence in the normal state and a resonance feature in the superconducting state of several Fe-based superconductors. Based on these findings, we develop a model of electrons interacting with a temperature dependent magnetic excitation spectrum and apply it to angle resolved photoemission in Ba(1-x)K(x)Fe(2)As(2). We reproduce in quantitative agreement with experiment a renormalization of the quasiparticle dispersion both in the normal and the superconducting state, and the dependence of the quasiparticle linewidth on binding energy.

Is CrO2 fully spin polarized? Analysis of Andreev spectra and excess current.

We report an extensive theoretical analysis of point-contact Andreev reflection data available in the literature on ferromagnetic CrO2. We find that the spectra can be well understood within a model of fully spin-polarized bands in CrO2 together with spin-active scattering at the contact. This is in contrast to analysis of the data within extended Blonder-Tinkham-Klapwijk models, which lead to a spin polarization varying between 50% and 100% depending on the transparency of the interface.