de Haas-van Alphen spectroscopy and fractional quantization of magnetic-breakdown orbits in moiré graphene
arXiv:2310.20338 · doi:10.1126/science.adh3499
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 moiré graphene. Scanning by SQUID-on-tip in Bernal bilayer graphene crystal-axis-aligned to hBN reveals abnormally large magnetization oscillations with amplitudes reaching 500 μ_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 moiré 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.
30 pages, 5 main text figures, 6 supplementary figures
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Cited by in corpus (7)
- A Microscopic Perspective on Moiré Materials
- Imaging Coulomb interactions and migrating Dirac cones in twisted graphene by local quantum oscillations
- High-mobility compensated semimetals, orbital magnetization, and umklapp scattering in bilayer graphene moire superlattices
- Interplay of valley, layer and band topology towards interacting quantum phases in moiré bilayer graphene
- Visualizing isospin magnetic texture and intervalley exchange interaction in rhombohedral tetralayer graphene
- Hexagonal boron nitride/bilayer graphene moiré superlattices in the Dirac-material family: energy-band engineering and carrier doping by dual gating
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