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<p>Moiré materials represent strongly interacting electron systems bridging topological and correlated physics. Despite notable advances, decoding wavefunction properties underlying the quantum geometry remains challenging. Here we utilize polarization-resolved photocurrent measurements to probe magic-angle twisted bilayer graphene, leveraging its sensitivity to the Berry connection that encompasses quantum ‘textures’ of electron wavefunctions. Using terahertz light resonant with optical transitions of its flat bands, we observe bulk photocurrents driven by broken symmetries and reveal the interplay between electron interactions and quantum geometry. We observe inversion-breaking gapped states undetectable through quantum transport, sharp changes in the polarization axes caused by interaction-induced band renormalization and recurring photocurrent patterns at integer filling factors of the moiré unit cell that track the evolution of quantum geometry through the cascade of phase transitions. The large and tunable terahertz response intrinsic to flat-band systems offers direct insights into the quantum geometry of interacting electrons and paves the way for innovative terahertz quantum technologies.</p>

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Terahertz photocurrent probe of quantum geometry and interactions in magic-angle twisted bilayer graphene

  • 期刊论文

  • 发表日期：

    2025年3月24日

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  • Roshan Krishna Kumar,
  • Geng Li,
  • Riccardo Bertini,
  • Swati Chaudhary,
  • Krystian Nowakowski,
  • Jeong Min Park,
  • Sebastian Castilla,
  • Zhen Zhan,
  • Pierre A. Pantaleón,
  • Hitesh Agarwal,
  • Sergi Batlle-Porro,
  • Eike Icking,
  • Matteo Ceccanti,
  • Antoine Reserbat-Plantey,
  • Giulia Piccinini,
  • Julien Barrier,
  • Ekaterina Khestanova,
  • Takashi Taniguchi,
  • Kenji Watanabe,
  • Christoph Stampfer,
  • Gil Refael,
  • Francisco Guinea,
  • Pablo Jarillo-Herrero,
  • Justin C. W. Song,
  • Petr Stepanov,
  • Cyprian Lewandowski,
  • Frank H. L. Koppens

摘要

Moiré materials represent strongly interacting electron systems bridging topological and correlated physics. Despite notable advances, decoding wavefunction properties underlying the quantum geometry remains challenging. Here we utilize polarization-resolved photocurrent measurements to probe magic-angle twisted bilayer graphene, leveraging its sensitivity to the Berry connection that encompasses quantum ‘textures’ of electron wavefunctions. Using terahertz light resonant with optical transitions of its flat bands, we observe bulk photocurrents driven by broken symmetries and reveal the interplay between electron interactions and quantum geometry. We observe inversion-breaking gapped states undetectable through quantum transport, sharp changes in the polarization axes caused by interaction-induced band renormalization and recurring photocurrent patterns at integer filling factors of the moiré unit cell that track the evolution of quantum geometry through the cascade of phase transitions. The large and tunable terahertz response intrinsic to flat-band systems offers direct insights into the quantum geometry of interacting electrons and paves the way for innovative terahertz quantum technologies.