Krishna Kumar Roshan, Li Geng, Bertini Riccardo, Chaudhary Swati, Nowakowski Krystian, Park Jeong Min, Castilla Sebastian, Zhan Zhen, Pantaleón Pierre A, Agarwal Hitesh, Batlle-Porro Sergi, Icking Eike, Ceccanti Matteo, Reserbat-Plantey Antoine, Piccinini Giulia, Barrier Julien, Khestanova Ekaterina, Taniguchi Takashi, Watanabe Kenji, Stampfer Christoph, Refael Gil, Guinea Francisco, Jarillo-Herrero Pablo, Song Justin C W, Stepanov Petr, Lewandowski Cyprian, Koppens Frank H L
ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels (Barcelona), Spain.
Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, Spain.
Nat Mater. 2025 Mar 24. doi: 10.1038/s41563-025-02180-3.
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.
莫尔材料代表了连接拓扑物理和关联物理的强相互作用电子系统。尽管取得了显著进展，但解码量子几何背后的波函数特性仍然具有挑战性。在这里，我们利用偏振分辨光电流测量来探测魔角扭曲双层石墨烯，利用其对包含电子波函数量子“纹理”的贝里联络的敏感性。通过太赫兹光与平带的光学跃迁共振，我们观察到由对称性破缺驱动的体光电流，并揭示了电子相互作用和量子几何之间的相互作用。我们观察到通过量子输运无法检测到的反演破缺带隙态、由相互作用诱导的能带重整化引起的偏振轴的急剧变化，以及在莫尔晶胞的整数填充因子处重复出现的光电流模式，这些模式通过相变级联跟踪量子几何的演化。平带系统固有的大且可调谐的太赫兹响应为深入了解相互作用电子的量子几何提供了直接见解，并为创新的太赫兹量子技术铺平了道路。
