Heavy electron doping induced antiferromagnetic phase as the parent for the iron oxypnictide superconductor LaFeAsO1−xHx

Abstract

We perform transport measurements and band structure calculations of electron-doped LaFeAsO1−xHx over a wide range of x from 0.01 to 0.66. The T2 and √T dependency of the resistivity are observed at x∼0.17 and 0.41, respectively. The sign change of RH without opening of the spin-density-wave gap for 0.45≤x≤0.58 and T<TN as well as the calculated non-nested Fermi surface at x=0.5 indicate the more localized nature of the AF2 as compared to spin-density-wave phase at the nondoped sample. Considering the results from band calculations and the finite size of Hund's rule coupling, the change of the normal conducting state with x is reasonably explained by a strong depression of the coherent scale owing to the increased effective Coulomb repulsion in the narrow antibonding 3dxy band that approaches the half-filled regime. The following transition from the paramagnet to AF2 is understood as the quenching or ordering of the less-screened spins with a large entropy at low temperature. These results suggest that the normal conducting properties over a wide doping range for the LaFeAsO1−xHx are strongly influenced by the local spins in the incoherent region. Thus, we conclude that the parent phase in LaFeAsO1−xHx is not the spin-density wave but the AF2, which may be primarily responsible for the singular superconducting properties of the 1111 type compared with other iron pnictides.

Source-reported materials — not catalogue approval

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