Electronic structure of nickelate superconductor NdNiO2Hx (x=0, 0.25, 0.5) under different strains

Abstract

The discovery of superconductivity in infinite-layer nickelates has drawn considerable attention and boosted numerous theoretical and experimental studies. Here, combining density functional theory and Wannier function calculations, we study the electronic structure of nickelate NdNiO2Hx (x=0, 0.25, 0.5) (NNOH) under five different in-plane strains. We unveil that, with H introduced, the orbital occupation of Ni 3dx2−y2 increases, accompanied by the shift of band structure toward lower energy under constant strain. Meanwhile, the H 1s orbital hybridizes and forms a bonding-antibonding state with the Ni 3dz2 orbital, reducing the occupation of the Ni 3dz2 orbital, which results in the decreased filling of Ni 3d orbital. By contrast, the strain has negligible influences on the filling of Ni 3d and Ni eg orbital polarization. As the H concentration increases, the contribution of the itinerant interstitial s (IIS) orbital to the band structure near the Fermi level gradually decreases and disappears at x=0.5 due to the doped H obliterating the IIS band. In addition, with compressive strain applied, the bandwidth of the Ni 3dx2−y2 orbital increases, consistent with the calculated stronger effective Ni 3dx2−y2 nearest-neighboring hopping. In addition, we find that the impact of H concentration and strain on the projected orbitals and calculated density of states is slight. Also, the influences of the Sr concentration (0–20%) and Hubbard U parameter on the electronic properties of NNO without strain are explored and found not to change the main conclusions.

Source-reported materials — not catalogue approval

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