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Title: Experimental realization of two-dimensional Dirac nodal line fermions in monolayer Cu2Si

Abstract

Topological nodal line semimetals, a novel quantum state of materials, possess topologically nontrivial valence and conduction bands that touch at a line near the Fermi level. The exotic band structure can lead to various novel properties, such as long-range Coulomb interaction and flat Landau levels. Recently, topological nodal lines have been observed in several bulk materials, such as PtSn4, ZrSiS, TlTaSe2 and PbTaSe2. However, in two-dimensional materials, experimental research on nodal line fermions is still lacking. Here, we report the discovery of two-dimensional Dirac nodal line fermions in monolayer Cu2Si based on combined theoretical calculations and angle-resolved photoemission spectroscopy measurements. The Dirac nodal lines in Cu2Si form two concentric loops centred around the Γ point and are protected by mirror reflection symmetry. In conclusion, our results establish Cu2Si as a platform to study the novel physical properties in two-dimensional Dirac materials and provide opportunities to realize high-speed low-dissipation devices.

Authors:
ORCiD logo [1];  [2];  [3];  [3];  [4]; ORCiD logo [2];  [5]; ORCiD logo [6];  [7]; ORCiD logo [7]; ORCiD logo [7];  [6];  [3];  [8];  [6];  [6];  [6];  [4];  [4];  [2] more »;  [3] « less
  1. Univ. of Tokyo,Tokyo (Japan); Hiroshima Univ., Hiroshima (Japan)
  2. Beijing Inst. of Technology, Beijing (China)
  3. Univ. of Tokyo,Tokyo (Japan)
  4. Chinese Academy of Sciences (CAS), Beijing (China)
  5. Hiroshima Univ., Hiroshima (Japan); Chinese Academy of Sciences (CAS), Beijing (China)
  6. Hiroshima Univ., Hiroshima (Japan)
  7. Istituto di Struttura della Materia (ISM), Trieste (Italy)
  8. Univ. of Illinois, Chicago, IL (United States)
Publication Date:
Research Org.:
Univ. of Illinois, Chicago, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
OSTI Identifier:
1499693
Grant/Contract Number:  
FG02-07ER46383
Resource Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 8; Journal Issue: 1; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Feng, Baojie, Fu, Botao, Kasamatsu, Shusuke, Ito, Suguru, Cheng, Peng, Liu, Cheng-Cheng, Feng, Ya, Wu, Shilong, Mahatha, Sanjoy K., Sheverdyaeva, Polina, Moras, Paolo, Arita, Masashi, Sugino, Osamu, Chiang, Tai-Chang, Shimada, Kenya, Miyamoto, Koji, Okuda, Taichi, Wu, Kehui, Chen, Lan, Yao, Yugui, and Matsuda, Iwao. Experimental realization of two-dimensional Dirac nodal line fermions in monolayer Cu2Si. United States: N. p., 2017. Web. https://doi.org/10.1038/s41467-017-01108-z.
Feng, Baojie, Fu, Botao, Kasamatsu, Shusuke, Ito, Suguru, Cheng, Peng, Liu, Cheng-Cheng, Feng, Ya, Wu, Shilong, Mahatha, Sanjoy K., Sheverdyaeva, Polina, Moras, Paolo, Arita, Masashi, Sugino, Osamu, Chiang, Tai-Chang, Shimada, Kenya, Miyamoto, Koji, Okuda, Taichi, Wu, Kehui, Chen, Lan, Yao, Yugui, & Matsuda, Iwao. Experimental realization of two-dimensional Dirac nodal line fermions in monolayer Cu2Si. United States. https://doi.org/10.1038/s41467-017-01108-z
Feng, Baojie, Fu, Botao, Kasamatsu, Shusuke, Ito, Suguru, Cheng, Peng, Liu, Cheng-Cheng, Feng, Ya, Wu, Shilong, Mahatha, Sanjoy K., Sheverdyaeva, Polina, Moras, Paolo, Arita, Masashi, Sugino, Osamu, Chiang, Tai-Chang, Shimada, Kenya, Miyamoto, Koji, Okuda, Taichi, Wu, Kehui, Chen, Lan, Yao, Yugui, and Matsuda, Iwao. Wed . "Experimental realization of two-dimensional Dirac nodal line fermions in monolayer Cu2Si". United States. https://doi.org/10.1038/s41467-017-01108-z. https://www.osti.gov/servlets/purl/1499693.
@article{osti_1499693,
title = {Experimental realization of two-dimensional Dirac nodal line fermions in monolayer Cu2Si},
author = {Feng, Baojie and Fu, Botao and Kasamatsu, Shusuke and Ito, Suguru and Cheng, Peng and Liu, Cheng-Cheng and Feng, Ya and Wu, Shilong and Mahatha, Sanjoy K. and Sheverdyaeva, Polina and Moras, Paolo and Arita, Masashi and Sugino, Osamu and Chiang, Tai-Chang and Shimada, Kenya and Miyamoto, Koji and Okuda, Taichi and Wu, Kehui and Chen, Lan and Yao, Yugui and Matsuda, Iwao},
abstractNote = {Topological nodal line semimetals, a novel quantum state of materials, possess topologically nontrivial valence and conduction bands that touch at a line near the Fermi level. The exotic band structure can lead to various novel properties, such as long-range Coulomb interaction and flat Landau levels. Recently, topological nodal lines have been observed in several bulk materials, such as PtSn4, ZrSiS, TlTaSe2 and PbTaSe2. However, in two-dimensional materials, experimental research on nodal line fermions is still lacking. Here, we report the discovery of two-dimensional Dirac nodal line fermions in monolayer Cu2Si based on combined theoretical calculations and angle-resolved photoemission spectroscopy measurements. The Dirac nodal lines in Cu2Si form two concentric loops centred around the Γ point and are protected by mirror reflection symmetry. In conclusion, our results establish Cu2Si as a platform to study the novel physical properties in two-dimensional Dirac materials and provide opportunities to realize high-speed low-dissipation devices.},
doi = {10.1038/s41467-017-01108-z},
journal = {Nature Communications},
number = 1,
volume = 8,
place = {United States},
year = {2017},
month = {10}
}

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Figures / Tables:

Fig. 1 Fig. 1 : Atomic and band structures of free-standing Cu2Si. a Top and side view. The orange and blue balls represent Cu and Si atoms, respectively. b, c Calculated band structures of Cu2Si without and with spin-orbit coupling (SOC), respectively. The vertical axis $E-E$$F$ corresponds to -$E$$B$, where $E$$B$ ismore » the binding energy. For simplicity, we label the three bands that cross the Fermi level $α$, $β$, and $γ$, respectively. The parity of mirror reflection symmetry for each band is labelled plus and minus signs in b. The zoom-in band structures in the blue and red ellipses are shown in g, h. d Band structure of Cu2Si after artificially increasing the intrinsic SOC by 20 times. e Fermi surface of Cu2Si without SOC. The blue, orange, and green lines correspond to bands $α, β$, and $γ$, respectively. f Momentum distribution of the nodal loops: NL1 (blue) and NL2 (orange). g, h Zoom-in band structures in the blue and red ellipses in c, which clearly show the SOC-induced gaps« less

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