Doping dependence of Hall coefficient and evolution of coherent electronic state in the normal state of the Fe-based superconductor Ba _1-xK _xFe ₂As ₂

We investigated the in-plane transport properties of the Fe-based superconductor Ba _1-xK _xFe ₂As ₂ with a wide composition range 0≤x≤0.55. We show that the doping dependence of the Hall coefficient is well described by the Boltzmann equation for a two-band system with a rigid-band approximation. We successfully deduced transport parameters, which suggested that holes with heavier mass conduct more smoothly than electrons. Moreover, the temperature variation of the Hall coefficient indicated that an anomalous coherent state characterized by heavy quasiparticles in hole bands evolved below ∼100 K, predominantly in the optimal and overdoped regions. We argue that this phenomenon can be understood in relation to the pseudopeak structure observed in angle-resolved photoemission spectroscopy.