{
  "id": "1205.3654",
  "version": "v1",
  "published": "2012-05-16T12:25:36.000Z",
  "updated": "2012-05-16T12:25:36.000Z",
  "title": "Unexpected mass acquisition of Dirac fermions at the quantum phase transition of a topological insulator",
  "authors": [
    "T. Sato",
    "Kouji Segawa",
    "K. Kosaka",
    "S. Souma",
    "K. Nakayama",
    "K. Eto",
    "T. Minami",
    "Yoichi Ando",
    "T. Takahashi"
  ],
  "comment": "Main Manuscript: 16 pages, 3 figures; Supplementary Information: 8 pages, 8 figures",
  "journal": "Nature Physics 7,840 (2011)",
  "doi": "10.1038/nphys2058",
  "categories": [
    "cond-mat.mes-hall",
    "cond-mat.str-el"
  ],
  "abstract": "The three-dimensional (3D) topological insulator is a novel quantum state of matter where an insulating bulk hosts a linearly-dispersing surface state, which can be viewed as a sea of massless Dirac fermions protected by the time-reversal symmetry (TRS). Breaking the TRS by a magnetic order leads to the opening of a gap in the surface state and consequently the Dirac fermions become massive. It has been proposed theoretically that such a mass acquisition is necessary for realizing novel topological phenomena, but achieving a sufficiently large mass is an experimental challenge. Here we report an unexpected discovery that the surface Dirac fermions in a solid-solution system TlBi(S1-xSex)2 acquires a mass without explicitly breaking the TRS. We found that this system goes through a quantum phase transition from the topological to the non-topological phase, and by tracing the evolution of the electronic states using the angle-resolved photoemission, we observed that the massless Dirac state in TlBiSe2 switches to a massive state before it disappears in the non-topological phase. This result suggests the existence of a condensed-matter version of the \"Higgs mechanism\" where particles acquire a mass through spontaneous symmetry breaking.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2012-05-16T12:25:36.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "quantum phase transition",
      "unexpected mass acquisition",
      "topological insulator",
      "surface state",
      "massless dirac"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "journal": "Nature Physics",
      "year": 2011,
      "month": "Nov",
      "volume": 7,
      "number": 11,
      "pages": 840
    },
    "note": {
      "typesetting": "TeX",
      "pages": 16,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1115534,
      "adsabs": "2011NatPh...7..840S"
    }
  }
}