We discuss the Josephson effect in strongly spin-polarized ferromagnets where triplet correlations are induced by means of spin-active interface scattering, extending our earlier work [Phys. Rev. Lett. 102, 227005 (2009)] by including impurity scatte
ring in the ferromagnetic bulk and the inverse proximity effect in a fully self-consistent way. Our quasiclassical approach accounts for the differences of Fermi momenta and Fermi velocities between the two spin bands of the ferromagnet, and thereby overcomes an important short-coming of previous work within the framework of Usadel theory. We show that non-magnetic disorder in conjunction with spin-dependent Fermi velocities may induce a reversal of the spin-current as a function of temperature.
The pairing mechanism in the iron-pnictide superconductors is still unknown. However, similarities to the cuprate high-temperature superconductors suggest that a similar mechanism may be at work. Recently, careful experimental studies of the spin exc
itation spectrum revealed, like in the cuprates, a strong temperature dependence in the normal state and a resonance feature in the superconducting state. Motivated by these findings, we develop a model of electrons interacting with a temperature dependent magnetic excitation spectrum based on these experimental observations. We apply it to analyse angle resolved photoemission and tunnelling spectra in Ba{1-x}KxFe2As2. We reproduce in quantitative agreement with experiment a renormalisation of the quasiparticle dispersion both in the normal and the superconducting state, and the dependence of the quasiparticle linewidth on binding energy. We estimate the strength of the coupling between electronic and spin excitations. Our findings support the possibility of a pairing mechanism based dominantly on such a coupling.
