{
  "id": "2403.08390",
  "version": "v1",
  "published": "2024-03-13T10:09:23.000Z",
  "updated": "2024-03-13T10:09:23.000Z",
  "title": "Sub-100-fs formation of dark excitons in monolayer WS$_2$",
  "authors": [
    "Pavel V. Kolesnichenko",
    "Lukas Wittenbecher",
    "Qianhui Zhang",
    "Run Yan Teh",
    "Chandni Babu",
    "Michael S. Fuhrer",
    "Anders Mikkelsen",
    "Donatas Zigmantas"
  ],
  "comment": "22 pages, 3 figures, 1 supplementary",
  "categories": [
    "cond-mat.mes-hall",
    "cond-mat.mtrl-sci",
    "physics.app-ph"
  ],
  "abstract": "Two-dimensional semiconductors based on transition metal dichalcogenides are promising for electronics and optoelectronics applications owing to their properties governed by strongly-bound bright and dark excitons. Momentum-forbidden dark excitons have recently received attention as better alternatives to bright excitons for long-range transport. However, accessing the dynamics of dark excitons is challenging experimentally. The most direct, but very complicated, experiment is transient angle-resolved photoemission electron spectroscopy: sub-100-fs formation of K-$\\Lambda$-excitons in monolayer WS$_2$ has been identified previously taking advantage of momentum resolution of detected signals [1]. Here, we use a simpler setting of transient photoemission electron microscopy (with spatial resolution of 75 nm), which is inherently sensitive to dark K-$\\Lambda$ excitons in monolayers of transition metal dichalcogenide and has exceptionally high temporal resolution of 13 fs. We are able to directly observe intervalley scattering (dark-exciton formation) in monolayer WS$_2$ with scattering rates in the range of 14-50 fs followed by picosecond-scale dynamics mediated by defects.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-03-13T10:09:23.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "monolayer ws",
      "transition metal dichalcogenide",
      "transient photoemission electron microscopy",
      "transient angle-resolved photoemission electron spectroscopy",
      "exceptionally high temporal resolution"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 22,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}