Ultrafast unbalanced electron distributions in quasicrystalline 30° twisted bilayer graphene

Takeshi Suzuki, Takushi Iimori, Sung Joon Ahn, Yuhao Zhao, Mari Watanabe, Jiadi Xu, Masami Fujisawa, Teruto Kanai, Nobuhisa Ishii, Jiro Itatani, Kento Suwa, Hirokazu Fukidome, Satoru Tanaka, Joung Real Ahn, Kozo Okazaki, Shik Shin, Fumio Komori, Iwao Matsuda

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Ultrafast carrier dynamics in a graphene system are very important in terms of optoelectronic devices. Recently, a twisted bilayer graphene has been discovered that possesses interesting electronic properties owing to strong modifications in interlayer couplings. Thus, a better understanding of ultrafast carrier dynamics in a twisted bilayer graphene is highly desired. Here, we reveal the unbalanced electron distributions in a quasicrystalline 30° twisted bilayer graphene (QCTBG), using time- A nd angle-resolved photoemission spectroscopy on the femtosecond time scale. We distinguish time-dependent electronic behavior between the upper- A nd lower-layer Dirac cones and gain insight into the dynamical properties of replica bands, which show characteristic signatures due to Umklapp scatterings. The experimental results are reproduced by solving a set of rate equations among the graphene layers and substrate. We find that the substrate buffer layer plays a key role in initial carrier injections to the upper and lower layers. Our results demonstrate that QCTBG can be a promising element for future devices.

Original languageEnglish
Pages (from-to)11981-11987
Number of pages7
JournalACS nano
Volume13
Issue number10
DOIs
Publication statusPublished - Oct 22 2019

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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    Suzuki, T., Iimori, T., Ahn, S. J., Zhao, Y., Watanabe, M., Xu, J., Fujisawa, M., Kanai, T., Ishii, N., Itatani, J., Suwa, K., Fukidome, H., Tanaka, S., Ahn, J. R., Okazaki, K., Shin, S., Komori, F., & Matsuda, I. (2019). Ultrafast unbalanced electron distributions in quasicrystalline 30° twisted bilayer graphene. ACS nano, 13(10), 11981-11987. https://doi.org/10.1021/acsnano.9b06091