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arXiv · 2310.20338

de Haas-van Alphen spectroscopy and fractional quantization of magnetic-breakdown orbits in moir\'e graphene

Matan Bocarsly·Matan Uzan·Indranil Roy·Sameer Grover·Jiewen Xiao·Zhiyu Dong·Mikhail Labendik·Aviram Uri·Martin E. Huber·Yuri Myasoedov·Kenji Watanabe·Takashi Taniguchi·Binghai Yan·Leonid S. Levitov·Eli Zeldov
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Abstract

Quantum oscillations originating from the quantization of the electron cyclotron orbits provide ultrasensitive diagnostics of electron bands and interactions in novel materials. We report on the first direct-space nanoscale imaging of the thermodynamic magnetization oscillations due to the de Haas-van Alphen effect in moir\'e graphene. Scanning by SQUID-on-tip in Bernal bilayer graphene crystal-axis-aligned to hBN reveals abnormally large magnetization oscillations with amplitudes reaching 500 {\mu}_B/electron in weak magnetic fields, unexpectedly low frequencies, and high sensitivity to the superlattice filling fraction. The oscillations allow us to reconstruct the complex band structure in exquisite detail, revealing narrow moir\'e bands with multiple overlapping Fermi surfaces separated by unusually small momentum gaps. We identify distinct sets of oscillations that violate the textbook Onsager Fermi surface sum rule, signaling formation of exotic broad-band particle-hole superposition states induced by coherent magnetic breakdown.

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Matan Bocarsly, Matan Uzan, Indranil Roy, Sameer Grover, Jiewen Xiao, Zhiyu Dong, Mikhail Labendik, Aviram Uri, Martin E. Huber, Yuri Myasoedov, Kenji Watanabe, Takashi Taniguchi, Binghai Yan, Leonid S. Levitov, Eli Zeldov. 2023-10-31. de Haas-van Alphen spectroscopy and fractional quantization of magnetic-breakdown orbits in moir\'e graphene. https://doi.org/10.1126/science.adh3499

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