{
  "id": "1412.8128",
  "version": "v1",
  "published": "2014-12-28T08:18:18.000Z",
  "updated": "2014-12-28T08:18:18.000Z",
  "title": "Optical Phonons in Twisted Bilayer Graphene with Gate-Induced Asymmetric Doping",
  "authors": [
    "Ting-Fung Chung",
    "Rui He",
    "Tai-Lung Wu",
    "Yong P. Chen"
  ],
  "comment": "27 pages, 4 figures, and 8 pages Suppl. Info",
  "categories": [
    "cond-mat.mes-hall",
    "cond-mat.mtrl-sci"
  ],
  "abstract": "Twisted bilayer graphene (tBLG) devices with ion gel gate dielectrics are studied using Raman spectroscopy in the twist angle regime where a resonantly enhanced G band can be observed. We observe prominent splitting and intensity quenching on the G Raman band when the carrier density is tuned away from charge neutrality. This G peak splitting is attributed to asymmetric charge doping in the two graphene layers, which reveals individual phonon self-energy renormalization of the two weakly-coupled layers of graphene. We estimate the effective interlayer capacitance at low doping density of tBLG using an interlayer screening model. The anomalous intensity quenching of both G peaks is ascribed to the suppression of resonant interband transitions between the two saddle points (van Hove singularities), that are displaced in the momentum space by gate-tuning. In addition, we observe a softening (hardening) of the R Raman band, a superlattice-induced phonon mode in tBLG, in electron (hole) doping. Our results demonstrate that gate modulation can be used to control the optoelectronic and vibrational properties in tBLG devices.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2014-12-28T08:18:18.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "twisted bilayer graphene",
      "gate-induced asymmetric doping",
      "optical phonons",
      "individual phonon self-energy renormalization",
      "raman band"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1021/nl504318a",
      "journal": "Nano Letters",
      "year": 2015,
      "month": "Feb",
      "volume": 15,
      "number": 2,
      "pages": 1203
    },
    "note": {
      "typesetting": "TeX",
      "pages": 27,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2015NanoL..15.1203C"
    }
  }
}