{
  "id": "cond-mat/0506800",
  "version": "v1",
  "published": "2005-06-30T13:18:39.000Z",
  "updated": "2005-06-30T13:18:39.000Z",
  "title": "AC Conductance in Dense Array of the Ge$_{0.7}$Si$_{0.3}$ Quantum Dots in Si",
  "authors": [
    "I. L. Drichko",
    "A. M. Diakonov",
    "I. Yu. Smirnov",
    "A. V. Suslov",
    "Y. M. Galperin",
    "A. I. Yakimov",
    "A. I. Nikiforov"
  ],
  "comment": "revtex, 3 pages, 6 figures",
  "doi": "10.1063/1.2355286",
  "categories": [
    "cond-mat.mes-hall"
  ],
  "abstract": "Complex AC-conductance, $\\sigma^{AC}$, in the systems with dense Ge$_{0.7}$Si$_{0.3}$ quantum dot (QD) arrays in Si has been determined from simultaneous measurements of attenuation, $\\Delta\\Gamma=\\Gamma(H)-\\Gamma(0)$, and velocity, $\\Delta V /V=(V(H)-V(0)) / V(0)$, of surface acoustic waves (SAW) with frequencies $f$ = 30-300 MHz as functions of transverse magnetic field $H \\leq$ 18 T in the temperature range $T$ = 1-20 K. It has been shown that in the sample with dopant (B) concentration 8.2$ \\times 10^{11}$ cm$^{-2}$ at temperatures $T \\leq$4 K the AC conductivity is dominated by hopping between states localized in different QDs. The observed power-law temperature dependence, $\\sigma_1(H=0)\\propto T^{2.4}$, and weak frequency dependence, $\\sigma_1(H=0)\\propto \\omega^0$, of the AC conductivity are consistent with predictions of the two-site model for AC hopping conductivity for the case of $\\omega \\tau_0 \\gg $1, where $\\omega=2\\pi f$ is the SAW angular frequency and $\\tau_0$ is the typical population relaxation time. At $T >$ 7 K the AC conductivity is due to thermal activation of the carriers (holes) to the mobility edge. In intermediate temperature region 4$ < T<$ 7 K, where AC conductivity is due to a combination of hops between QDs and diffusion on the mobility edge, one succeeded to separate both contributions. Temperature dependence of hopping contribution to the conductivity above $T^*\\sim$ 4.5 K saturates, evidencing crossover to the regime where $\\omega \\tau_0 < $1. From crossover condition, $\\omega \\tau_0(T^*)$ = 1, the typical value, $\\tau_0$, of the relaxation time has been determined.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2005-06-30T13:18:39.000Z"
    }
  ],
  "analyses": {
    "subjects": [
      "73.63.Kv",
      "72.80.Jc",
      "72.20.Ee",
      "72.20.My",
      "72.50.+b"
    ],
    "keywords": [
      "quantum dot",
      "dense array",
      "ac conductivity",
      "ac conductance",
      "mobility edge"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "RevTeX",
      "pages": 3,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2006AIPC..850.1530D"
    }
  }
}