Normal state bottleneck and nematic fluctuations from femtosecond quasi-particle relaxation dynamics in Sm(Fe,Co)AsO

Abstract

We investigate temperature and fluence dependent dynamics of the photoexcited quasi-particle relaxation and low-energy electronic structure in electron-doped 1111-structure Sm(Fe_{0.93}Co_{0.07})AsO single crystal. We find that the behavior is qualitatively identical to the 122-structure Ba(Fe,Co)_{2}As_{2} including the presence of a normal state pseudogap and a marked 2-fold symmetry breaking in the tetragonal phase that we relate to the electronic nematicity. The 2-fold symmetry breaking appears to be a general feature of the electron doped iron pnictides.