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

doi:10.1021/acsnano.9b06091

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

Information Devices Division

Research output: Contribution to journal › Article › peer-review

23 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 language	English
Pages (from-to)	11981-11987
Number of pages	7
Journal	ACS Nano
Volume	13
Issue number	10
DOIs	https://doi.org/10.1021/acsnano.9b06091
Publication status	Published - 2019 Oct 22

Keywords

And optoelectronics
Graphene
Interfaces
Quasicrystal
Ultrafast dynamics
Valleytronics

ASJC Scopus subject areas

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

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10.1021/acsnano.9b06091

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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

Suzuki, T, Iimori, T, Ahn, SJ, Zhao, Y, Watanabe, M, Xu, J, Fujisawa, M, Kanai, T, Ishii, N, Itatani, J, Suwa, K, Fukidome, H, Tanaka, S, Ahn, JR, Okazaki, K, Shin, S, Komori, F & Matsuda, I 2019, 'Ultrafast unbalanced electron distributions in quasicrystalline 30° twisted bilayer graphene', ACS Nano, vol. 13, no. 10, pp. 11981-11987. https://doi.org/10.1021/acsnano.9b06091

@article{9832b9b90ec5401e92ec6ba1cb26610d,

title = "Ultrafast unbalanced electron distributions in quasicrystalline 30° twisted bilayer graphene",

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.",

keywords = "And optoelectronics, Graphene, Interfaces, Quasicrystal, Ultrafast dynamics, Valleytronics",

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

note = "Funding Information: We would like to acknowledge Y. Tsujikawa, M. Sakamoto, and A. Takayama for their kind support during the experiments. We would also like to thank M. Koshino, T. Ishimasa, K. Kimura, and E. Minamitani for valuable discussions and comments. This work was supported by Grants-in-Aid for Scientific Research (KAKENHI) (Grants 16H06361, 18H03874, 18K19011, 18K13498, 18H01146, 19H00659, 19H01818, and 19H00651) from Japan Society for the Promotion of Science (JSPS) and by JSPS KAKENHI on Innovative Areas “Quantum Liquid Crystals” (Grant 19H05826), and by Quantum Leap Flagship Program (Q-LEAP) (Grant JPMXS0118068681) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT). Publisher Copyright: Copyright {\textcopyright} 2019 American Chemical Society.",

year = "2019",

month = oct,

day = "22",

doi = "10.1021/acsnano.9b06091",

language = "English",

volume = "13",

pages = "11981--11987",

journal = "ACS Nano",

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T1 - Ultrafast unbalanced electron distributions in quasicrystalline 30° twisted bilayer graphene

AU - Suzuki, Takeshi

AU - Iimori, Takushi

AU - Ahn, Sung Joon

AU - Zhao, Yuhao

AU - Watanabe, Mari

AU - Xu, Jiadi

AU - Fujisawa, Masami

AU - Kanai, Teruto

AU - Ishii, Nobuhisa

AU - Itatani, Jiro

AU - Suwa, Kento

AU - Fukidome, Hirokazu

AU - Tanaka, Satoru

AU - Ahn, Joung Real

AU - Okazaki, Kozo

AU - Shin, Shik

AU - Komori, Fumio

AU - Matsuda, Iwao

N1 - Funding Information: We would like to acknowledge Y. Tsujikawa, M. Sakamoto, and A. Takayama for their kind support during the experiments. We would also like to thank M. Koshino, T. Ishimasa, K. Kimura, and E. Minamitani for valuable discussions and comments. This work was supported by Grants-in-Aid for Scientific Research (KAKENHI) (Grants 16H06361, 18H03874, 18K19011, 18K13498, 18H01146, 19H00659, 19H01818, and 19H00651) from Japan Society for the Promotion of Science (JSPS) and by JSPS KAKENHI on Innovative Areas “Quantum Liquid Crystals” (Grant 19H05826), and by Quantum Leap Flagship Program (Q-LEAP) (Grant JPMXS0118068681) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT). Publisher Copyright: Copyright © 2019 American Chemical Society.

PY - 2019/10/22

Y1 - 2019/10/22

N2 - 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.

AB - 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.

KW - And optoelectronics

KW - Graphene

KW - Interfaces

KW - Quasicrystal

KW - Ultrafast dynamics

KW - Valleytronics

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AN - SCOPUS:85073154476

SN - 1936-0851

VL - 13

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EP - 11987

JO - ACS Nano

JF - ACS Nano

IS - 10

ER -

Ultrafast unbalanced electron distributions in quasicrystalline 30° twisted bilayer graphene

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