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<p>In conventional superconductors, the formation of Cooper pairs is mediated by phonons. For the superconducting phases in moiré materials, such as that in twisted bilayer graphene, an unresolved question is whether pair formation is driven by electronic interactions, phonons or a combination of both. Here we show that, unlike conventional superconductors, the superconductivity in twisted bilayer graphene is strongly dependent on the dielectric environment. We place twisted bilayer graphene a short distance above a bulk SrTiO<sub>3</sub> substrate that has a large and tunable dielectric constant. By raising the dielectric constant in situ in both magic-angle and large-angle devices, we observe steady suppression and eventually a complete extinguishing of the entire superconducting dome. The experimental results are in qualitative agreement with a theoretical model in which the pairing mechanism arises from Coulomb interactions that are screened by plasmons, electron–hole pairs and longitudinal acoustic phonons. Our results highlight the unconventional nature of the superconductivity in this material, the double-edged role played by electronic interactions and the environment in its formation, and their complex interplay with the correlated insulating states.</p>

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Double-edged role of interactions in superconducting twisted bilayer graphene

  • 期刊论文

  • 发表日期：

    2026年4月7日

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  • Xueshi Gao,
  • Alejandro Jimeno-Pozo,
  • Pierre A. Pantaleon,
  • Aatmaj Rajesh,
  • Emilio Codecido,
  • Daria L. Sharifi,
  • Zheneng Zhang,
  • Youwei Liu,
  • Kenji Watanabe,
  • Takashi Taniguchi,
  • Marc W. Bockrath,
  • Francisco Guinea,
  • Chun Ning Lau

摘要

In conventional superconductors, the formation of Cooper pairs is mediated by phonons. For the superconducting phases in moiré materials, such as that in twisted bilayer graphene, an unresolved question is whether pair formation is driven by electronic interactions, phonons or a combination of both. Here we show that, unlike conventional superconductors, the superconductivity in twisted bilayer graphene is strongly dependent on the dielectric environment. We place twisted bilayer graphene a short distance above a bulk SrTiO3 substrate that has a large and tunable dielectric constant. By raising the dielectric constant in situ in both magic-angle and large-angle devices, we observe steady suppression and eventually a complete extinguishing of the entire superconducting dome. The experimental results are in qualitative agreement with a theoretical model in which the pairing mechanism arises from Coulomb interactions that are screened by plasmons, electron–hole pairs and longitudinal acoustic phonons. Our results highlight the unconventional nature of the superconductivity in this material, the double-edged role played by electronic interactions and the environment in its formation, and their complex interplay with the correlated insulating states.