{
  "id": "1504.02082",
  "version": "v1",
  "published": "2015-04-08T19:14:56.000Z",
  "updated": "2015-04-08T19:14:56.000Z",
  "title": "Exchange and collective behavior of magnetic impurities in a disordered helical metal",
  "authors": [
    "Hector Ochoa"
  ],
  "comment": "5 pages, 3 figures; comments are welcome",
  "categories": [
    "cond-mat.mes-hall",
    "cond-mat.str-el"
  ],
  "abstract": "We study the exchange interaction and the subsequent collective behavior of magnetic impurities embedded in a disordered two-dimensional (2D) helical metal. The exchange coupling follows a statistical distribution whose moments are calculated to the lowest order in $\\left(p_F\\ell\\right)^{-1}$, where $p_F$ is the Fermi momentum of itinerant electrons and $\\ell$ is the mean free path. We find that i) the first moment of the distribution decays exponentially, and ii) the variance of the interaction is long-range, however, it becomes independent of the orientation of the localized magnetic moments due to the locking between spin and momentum of the electrons that mediate the interaction. As consequence, long-range magnetic order tends to be suppressed, and a spin glass phase is stabilized at finite temperatures. The formalism is applied to the surface states of a three-dimensional (3D) topological insulator. The lack of a net magnetic moment in the glassy phase and the full randomization of spin polarization at distances larger than $\\ell$ excludes a spectral gap for surface states. Hence, non-magnetic disorder may explain the dispersion in results for photoemission experiments in magnetically-doped topological insulators.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-04-08T19:14:56.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "magnetic impurities",
      "disordered helical metal",
      "collective behavior",
      "surface states",
      "long-range magnetic order tends"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 5,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}