Lifetimes of Excited Electrons In Fe And Ni: First-Principles GW and theT-Matrix Theory

We present the results of an ab initio calculation of excited electron lifetimes in ferromagnetic materials which incorporates non-spin-flip and spin-flip processes within GW and $T$-matrix approaches. The method we develop is applied to low-energy electron excitations in Fe and Ni. It is found that the spin-wave generation in Fe essentially reduces the lifetimes of the spin-minority $d$ states whereas the free-electron-like spin-minority states and all the spin-majority states are affected much less. The influence of spin-flip scattering on the lifetimes in Ni appears to be weak. The $T$-matrix non-spin-flip processes are important for the lifetimes of excited spin-minority states.