{
  "id": "1510.02759",
  "version": "v1",
  "published": "2015-10-09T18:21:38.000Z",
  "updated": "2015-10-09T18:21:38.000Z",
  "title": "Topological semi-metals with line nodes and drumhead surface states",
  "authors": [
    "Y. -H. Chan",
    "Ching-Kai Chiu",
    "M. Y. Chou",
    "Andreas P. Schnyder"
  ],
  "comment": "16 pages, 8 figures",
  "categories": [
    "cond-mat.mes-hall",
    "cond-mat.mtrl-sci"
  ],
  "abstract": "In an ordinary three-dimensional metal the Fermi surface forms a two-dimensional closed sheet separating the filled from the empty states. Topological semimetals, on the other hand, can exhibit protected one-dimensional Fermi lines or zero-dimensional Fermi points, which arise due to an intricate interplay between symmetry and topology of the electronic wavefunctions. Here, we study how reflection symmetry, time-reversal symmetry, SU(2) spin-rotation symmetry, and inversion symmetry lead to the topological protection of line nodes in three-dimensional semi-metals. We obtain the crystalline invariants that guarantee the stability of the line nodes in the bulk and show that a quantized Berry phase leads to the appearance of protected surfaces states with a nearly flat dispersion. By deriving a relation between the crystalline invariants and the Berry phase, we establish a direct connection between the stability of the line nodes and the topological surface states. As a representative example of a topological semimetal with line nodes, we consider Ca$_3$P$_2$ and discuss the topological properties of its Fermi line in terms of a low-energy effective theory and a tight-binding model, derived from ab initio DFT calculations. Due to the bulk-boundary correspondence, Ca$_3$P$_2$ displays nearly dispersionless surface states, which take the shape of a drumhead. These surface states could potentially give rise to novel topological response phenomena and provide an avenue for exotic correlation physics at the surface.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-10-09T18:21:38.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "line nodes",
      "drumhead surface states",
      "topological semi-metals",
      "ab initio dft calculations",
      "berry phase"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 16,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2015arXiv151002759C"
    }
  }
}