Tunable ferromagnetism at non-integer filling of a moiré superlattice

Abstract

The flat bands resulting from moiré superlattices in magic-angle twisted bilayer graphene (MATBG) and ABC-trilayer graphene aligned with hexagonal boron nitride (ABC-TLG/hBN) have been shown to give rise to fascinating correlated electron phenomena such as correlated insulators and superconductivity. More recently, orbital magnetism associated with correlated Chern insulators was found in this class of layered structures centered at integer multiples of n0, the density corresponding to one electron per moiré superlattice unit cell. Here we report the experimental observation of ferromagnetism at fractional filling of a flat Chern band in an ABC-TLG/hBN moirésuperlattice. The ferromagnetic state exhibits prominent ferromagnetic hysteresis behavior with large anomalous Hall resistivity in a broad region of densities, centered in the valence miniband at n = -2.3 n0. This ferromagnetism depends very sensitively on the control parameters in the moiré system: not only the magnitude of the anomalous Hall signal, but also the sign of the hysteretic ferromagnetic response can be modulated by tuning the carrier density and displacement field. Our discovery of electrically tunable ferromagnetism in a moiré Chern band at non-integer filling highlights the opportunities for exploring new correlated ferromagnetic states in moiré heterostructures.

12 pages, 4 figures

References in corpus (3)

• Half and quarter metals in rhombohedral trilayer graphene
• Evidence of orbital ferromagnetism in twisted bilayer graphene aligned to hexagonal boron nitride
• Gate Tunable Magnetism and Giant Magnetoresistance in ABC-stacked Few-Layer Graphene

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• Quantum Metric Induced Phases in Moiré Materials
• Moiré Fractional Chern Insulators III: Hartree-Fock Phase Diagram, Magic Angle Regime for Chern Insulator States, the Role of the Moiré Potential and Goldstone Gaps in Rhombohedral Graphene Superlattices
• Intrinsic spin Hall torque in a moire Chern magnet
• Tunable quantum criticalities in an isospin extended Hubbard model simulator
• Helical trilayer graphene: a moiré platform for strongly-interacting topological bands
• Spin-orbit coupling-enhanced valley ordering of malleable bands in twisted bilayer graphene on WSe2
• Multiferroicity and Topology in Twisted Transition Metal Dichalcogenides
• Magnetic field stabilized Wigner crystal states in a graphene moiré superlattice
• Prediction of polarization vortices, charge modulation, flat bands, and moiré magnetism in twisted oxide bilayers
• Optical signatures of periodic magnetization: the moiré Zeeman effect
• Mott correlations in ABC graphene trilayer aligned with hBN
• Automated Tabletop Exfoliation and Identification of Monolayer Graphene Flakes
• Unveiling the Miniband Structure of Graphene Moiré Superlattices via Gate-dependent Terahertz Photocurrent Spectroscopy
• Insulators at Fractional Fillings in Twisted Bilayer Graphene Partially Aligned to Hexagonal Boron Nitride
• Non-Abelian Chern band in rhombohedral graphene multilayers
• Spin-orbit-driven quarter semimetals in rhombohedral graphene