{
  "id": "0801.0901",
  "version": "v1",
  "published": "2008-01-07T05:35:19.000Z",
  "updated": "2008-01-07T05:35:19.000Z",
  "title": "The Quantum Spin Hall Effect: Theory and Experiment",
  "authors": [
    "Markus Koenig",
    "Hartmut Buhmann",
    "Laurens W. Molenkamp",
    "Taylor L. Hughes",
    "Chao-Xing Liu",
    "Xiao-Liang Qi",
    "Shou-Cheng Zhang"
  ],
  "comment": "Invited review article for special issue of JPSJ, 32 pages. For higher resolution figures see official online version when published",
  "doi": "10.1143/JPSJ.77.031007",
  "categories": [
    "cond-mat.mes-hall"
  ],
  "abstract": "The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Recently, a new class of topological insulators has been proposed. These topological insulators have an insulating gap in the bulk, but have topologically protected edge states due to the time reversal symmetry. In two dimensions the helical edge states give rise to the quantum spin Hall (QSH) effect, in the absence of any external magnetic field. Here we review a recent theory which predicts that the QSH state can be realized in HgTe/CdTe semiconductor quantum wells. By varying the thickness of the quantum well, the band structure changes from a normal to an \"inverted\" type at a critical thickness $d_c$. We present an analytical solution of the helical edge states and explicitly demonstrate their topological stability. We also review the recent experimental observation of the QSH state in HgTe/(Hg,Cd)Te quantum wells. We review both the fabrication of the sample and the experimental setup. For thin quantum wells with well width $d_{QW}< 6.3$ nm, the insulating regime shows the conventional behavior of vanishingly small conductance at low temperature. However, for thicker quantum wells ($d_{QW}> 6.3$ nm), the nominally insulating regime shows a plateau of residual conductance close to $2e^2/h$. The residual conductance is independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance is destroyed by a small external magnetic field. The quantum phase transition at the critical thickness, $d_c= 6.3$ nm, is also independently determined from the occurrence of a magnetic field induced insulator to metal transition.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2008-01-07T05:35:19.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "quantum spin hall effect",
      "residual conductance",
      "helical edge states",
      "experiment",
      "small external magnetic field"
    ],
    "tags": [
      "review article",
      "journal article",
      "famous paper"
    ],
    "publication": {
      "journal": "Journal of the Physical Society of Japan",
      "year": 2008,
      "month": "Mar",
      "volume": 77,
      "number": 3,
      "pages": 31007
    },
    "note": {
      "typesetting": "TeX",
      "pages": 32,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2008JPSJ...77c1007K"
    }
  }
}