{
  "id": "1909.04657",
  "version": "v1",
  "published": "2019-09-10T17:59:51.000Z",
  "updated": "2019-09-10T17:59:51.000Z",
  "title": "Electronic structures and topological properties in nickelates $Ln_{n+1}$Ni$_n$O$_{2n+2}$",
  "authors": [
    "Jiacheng Gao",
    "Zhijun Wang",
    "Chen Fang",
    "Hongming Weng"
  ],
  "comment": "10 pages, 7 figures, 4 tables",
  "categories": [
    "cond-mat.mtrl-sci",
    "cond-mat.supr-con"
  ],
  "abstract": "After the significant discovery of the hole-doped nickelate compound Nd$_{0.8}$Sr$_{0.2}$NiO$_2$, an analysis of the electronic structure, orbital components, Fermi surfaces, and band topology could be helpful to understand the mechanism of its superconductivity. Based on the first-principles calculations, we find that Ni $3d_{x^2-y^2}$ states contribute the largest Fermi surface. $Ln~5d_{3z^2-r^2}$ states form an electron pocket at $\\Gamma$, while $5d_ {xy}$ states form a relatively bigger pocket at A. These Fermi surfaces and symmetries can be reproduced by our two-band model, which consists of two elementary band representations: $B_{1g}@1a~\\oplus~A_{1g}@1b$. By hole doping, a hole pocket originating from Ni $3d_{xy}$ orbital can be introduced, which may be related to the observed sign change of Hall coefficient. We find that there is a band inversion happened at A, which can be affected by the value of Coulomb interaction $U$ in the calculations. With small $U$ and spin-orbital coupling, it gives rise to a pair of Dirac points along A-M. By introducing an additional Ni $3d_{xy}$ orbital, the hole-pocket band and the possible band inversion can be captured in the modified model. Besides, the nontrivial band topology in the ferromagnetic two-layer compound La$_3$Ni$_2$O$_6$ is discussed and the band inversion is associated with Ni $3d_{x^2-y^2}$ and La $5d_{xy}$ orbitals.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-09-10T17:59:51.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "electronic structure",
      "topological properties",
      "band inversion",
      "states form",
      "ferromagnetic two-layer compound"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}