Crystalline anisotropy associated with a second antiferromagnetic phase in the absence of spin density wave in the heavily hydrogen-doped LaFeAsO1−xHx (x∼0.5)

Abstract

Electronic and magnetic properties of the heavily H-doped LaFeAsO1−xHx (x∼0.5) were studied in the framework of the density functional theory combined with the dynamical mean field theory. We found a stripe-like-ordered structure of hydrogen and oxygen atoms, as the ground state, in a 2 a×2b×c supercell, with the same configuration as the antiferromagnetic order. The new configuration could explain the existing experimental results related to the heavily H-doped LaFeAsO1−xHx, such as the in-plane electronic anisotropy and the nonuniform magnetic behavior. A significant anisotropy was observed between Fe-3dxz (xz) and Fe-3dyz (yz) orbitals in the ground state in the absence of the pseudogap resulting from the spin density wave phase, which was found to originate from the crystalline anisotropy. Magnetic moments were not spatially uniform and were sensitive to the crystal configuration. We found that the nonuniform magnetic behavior is associated with the As–Fe–As bond angle in the structure. Our findings would clarify the importance of crystal details and orbital degrees of freedom in iron-based superconductors.