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Title: Signatures of tunable superconductivity in a trilayer graphene moiré superlattice

Abstract

Understanding the mechanism of high-transition-temperature (high-Tc) superconductivity is a central problem in condensed matter physics. It is often speculated that high-Tc superconductivity arises in a doped Mott insulator1 as described by the Hubbard model2-4. An exact solution of the Hubbard model, however, is extremely challenging owing to the strong electron-electron correlation in Mott insulators. Therefore, it is highly desirable to study a tunable Hubbard system, in which systematic investigations of the unconventional superconductivity and its evolution with the Hubbard parameters can deepen our understanding of the Hubbard model. Here we report signatures of tunable superconductivity in an ABC-trilayer graphene (TLG) and hexagonal boron nitride (hBN) moiré superlattice. Unlike in 'magic angle' twisted bilayer graphene, theoretical calculations show that under a vertical displacement field, the ABC-TLG/hBN heterostructure features an isolated flat valence miniband associated with a Hubbard model on a triangular superlattice5,6 where the bandwidth can be tuned continuously with the vertical displacement field. Upon applying such a displacement field we find experimentally that the ABC-TLG/hBN superlattice displays Mott insulating states below 20 kelvin at one-quarter and one-half fillings of the states, corresponding to one and two holes per unit cell, respectively. Upon further cooling, signatures of superconductivity ('domes') emerge belowmore » 1 kelvin for the electron- and hole-doped sides of the one-quarter-filling Mott state. The electronic behaviour in the ABC-TLG/hBN superlattice is expected to depend sensitively on the interplay between the electron-electron interaction and the miniband bandwidth. By varying the vertical displacement field, we demonstrate transitions from the candidate superconductor to Mott insulator and metallic phases. Our study shows that ABC-TLG/hBN heterostructures offer attractive model systems in which to explore rich correlated behaviour emerging in the tunable triangular Hubbard model.« less

Authors:
 [1];  [2];  [1];  [2];  [3];  [4];  [5];  [5];  [6];  [6];  [7];  [5];  [3];  [8];  [1]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
  2. Stanford Univ., CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States)
  4. Univ. of California, Berkeley, CA (United States)
  5. Shanghai Jiao Tong Univ. (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing (China)
  6. National Inst. for Materials Science (NIMS), Tsukuba (Japan)
  7. Univ. of Seoul, Seoul (Korea, Republic of)
  8. Collaborative Innovation Center of Advanced Microstructures, Nanjing (China); Fudan Univ., Shanghai (China)
Publication Date:
Research Org.:
Stanford Univ., Redwood City, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
OSTI Identifier:
1545526
Alternate Identifier(s):
OSTI ID: 1619126
Grant/Contract Number:  
AC02-76SF00515; AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nature (London)
Additional Journal Information:
Journal Volume: 572; Journal Issue: 7768; Journal ID: ISSN 0028-0836
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Chen, Guorui, Sharpe, Aaron L., Gallagher, Patrick, Rosen, Ilan T., Fox, Eli J., Jiang, Lili, Lyu, Bosai, Li, Hongyuan, Watanabe, Kenji, Taniguchi, Takashi, Jung, Jeil, Shi, Zhiwen, Goldhaber-Gordon, David, Zhang, Yuanbo, and Wang, Feng. Signatures of tunable superconductivity in a trilayer graphene moiré superlattice. United States: N. p., 2019. Web. doi:10.1038/s41586-019-1393-y.
Chen, Guorui, Sharpe, Aaron L., Gallagher, Patrick, Rosen, Ilan T., Fox, Eli J., Jiang, Lili, Lyu, Bosai, Li, Hongyuan, Watanabe, Kenji, Taniguchi, Takashi, Jung, Jeil, Shi, Zhiwen, Goldhaber-Gordon, David, Zhang, Yuanbo, & Wang, Feng. Signatures of tunable superconductivity in a trilayer graphene moiré superlattice. United States. https://doi.org/10.1038/s41586-019-1393-y
Chen, Guorui, Sharpe, Aaron L., Gallagher, Patrick, Rosen, Ilan T., Fox, Eli J., Jiang, Lili, Lyu, Bosai, Li, Hongyuan, Watanabe, Kenji, Taniguchi, Takashi, Jung, Jeil, Shi, Zhiwen, Goldhaber-Gordon, David, Zhang, Yuanbo, and Wang, Feng. Wed . "Signatures of tunable superconductivity in a trilayer graphene moiré superlattice". United States. https://doi.org/10.1038/s41586-019-1393-y. https://www.osti.gov/servlets/purl/1545526.
@article{osti_1545526,
title = {Signatures of tunable superconductivity in a trilayer graphene moiré superlattice},
author = {Chen, Guorui and Sharpe, Aaron L. and Gallagher, Patrick and Rosen, Ilan T. and Fox, Eli J. and Jiang, Lili and Lyu, Bosai and Li, Hongyuan and Watanabe, Kenji and Taniguchi, Takashi and Jung, Jeil and Shi, Zhiwen and Goldhaber-Gordon, David and Zhang, Yuanbo and Wang, Feng},
abstractNote = {Understanding the mechanism of high-transition-temperature (high-Tc) superconductivity is a central problem in condensed matter physics. It is often speculated that high-Tc superconductivity arises in a doped Mott insulator1 as described by the Hubbard model2-4. An exact solution of the Hubbard model, however, is extremely challenging owing to the strong electron-electron correlation in Mott insulators. Therefore, it is highly desirable to study a tunable Hubbard system, in which systematic investigations of the unconventional superconductivity and its evolution with the Hubbard parameters can deepen our understanding of the Hubbard model. Here we report signatures of tunable superconductivity in an ABC-trilayer graphene (TLG) and hexagonal boron nitride (hBN) moiré superlattice. Unlike in 'magic angle' twisted bilayer graphene, theoretical calculations show that under a vertical displacement field, the ABC-TLG/hBN heterostructure features an isolated flat valence miniband associated with a Hubbard model on a triangular superlattice5,6 where the bandwidth can be tuned continuously with the vertical displacement field. Upon applying such a displacement field we find experimentally that the ABC-TLG/hBN superlattice displays Mott insulating states below 20 kelvin at one-quarter and one-half fillings of the states, corresponding to one and two holes per unit cell, respectively. Upon further cooling, signatures of superconductivity ('domes') emerge below 1 kelvin for the electron- and hole-doped sides of the one-quarter-filling Mott state. The electronic behaviour in the ABC-TLG/hBN superlattice is expected to depend sensitively on the interplay between the electron-electron interaction and the miniband bandwidth. By varying the vertical displacement field, we demonstrate transitions from the candidate superconductor to Mott insulator and metallic phases. Our study shows that ABC-TLG/hBN heterostructures offer attractive model systems in which to explore rich correlated behaviour emerging in the tunable triangular Hubbard model.},
doi = {10.1038/s41586-019-1393-y},
url = {https://www.osti.gov/biblio/1545526}, journal = {Nature (London)},
issn = {0028-0836},
number = 7768,
volume = 572,
place = {United States},
year = {2019},
month = {7}
}

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Works referenced in this record:

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    Correlated states in twisted double bilayer graphene
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    2D Materials for Large‐Area Flexible Thermoelectric Devices
    journal, November 2019


    Large-area epitaxial growth of curvature-stabilized ABC trilayer graphene
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    Strong correlations and orbital texture in single-layer 1T-TaSe2
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    journal, October 2019


    Tunable correlated Chern insulator and ferromagnetism in a moiré superlattice
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    journal, December 2019


    Pairing and non-Fermi liquid behavior in partially flat-band systems: Beyond nesting physics
    journal, January 2020


    Spin liquids and pseudogap metals in the SU(4) Hubbard model in a moiré superlattice
    journal, January 2020


    Topological sliding moiré heterostructure
    journal, January 2020


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    journal, January 2020


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