Abstract
The examination of the electrical resistivities of iron pnictides shows that they follow a ρ∼T exp(Ea/kBT) temperature dependence. The activation energies Ea show a linear behaviour with the critical temperatures of the spin density waves (SDW), T*, as both vary with pressure. The slope matches the ratio SDW gap to T*, while the intercept can be related to the transition temperature of the lattice distortion, T0. An adapted Landau free energy predicts the observed order of the transitions, according to which is higher, T* or T0. We discuss our analysis within the framework of polarons.
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