Half and quarter metals in rhombohedral trilayer graphene

Abstract

Ferromagnetism is most common in transition metal compounds but may also arise in low-density two-dimensional electron systems, with signatures observed in silicon, III-V semiconductor systems, and graphene moiré heterostructures. Here we show that gate-tuned van Hove singularities in rhombohedral trilayer graphene drive the spontaneous ferromagnetic polarization of the electron system into one or more spin- and valley flavors. Using capacitance measurements on graphite-gated van der Waals heterostructures, we find a cascade of density- and electronic displacement field tuned phase transitions marked by negative electronic compressibility. The transitions define the boundaries between phases where quantum oscillations have either four-fold, two-fold, or one-fold degeneracy, associated with a spin and valley degenerate normal metal, spin-polarized `half-metal', and spin and valley polarized `quarter metal', respectively. For electron doping, the salient features are well captured by a phenomenological Stoner model with a valley-anisotropic Hund's coupling, likely arising from interactions at the lattice scale. For hole filling, we observe a richer phase diagram featuring a delicate interplay of broken symmetries and transitions in the Fermi surface topology. Finally, by rotational alignment of a hexagonal boron nitride substrate to induce a moiré superlattice, we find that the superlattice perturbs the preexisting isospin order only weakly, leaving the basic phase diagram intact while catalyzing the formation of topologically nontrivial gapped states whenever itinerant half- or quarter metal states occur at half- or quarter superlattice band filling. Our results show that rhombohedral trilayer graphene is an ideal platform for well-controlled tests of many-body theory and reveal magnetism in moiré materials to be fundamentally itinerant in nature.

References in corpus (29)

• Berry Phase Effects on Electronic Properties
• Emergent ferromagnetism near three-quarters filling in twisted bilayer graphene
• Intrinsic quantized anomalous Hall effect in a moiré heterostructure
• Optical detection of Mott and generalized Wigner crystal states in WSe2/WS2 moiré superlattices
• Tunable Correlated Chern Insulator and Ferromagnetism in Trilayer Graphene/Boron Nitride Moiré Superlattice
• Signatures of Gate-Tunable Superconductivity in Trilayer Graphene/Boron Nitride Moiré Superlattice
• Abundance of correlated insulating states at fractional fillings of WSe${}_2$/WS${}_2$ moiré superlattices
• Evidence of Gate-Tunable Mott Insulator in Trilayer Graphene-Boron Nitride Moiré Superlattice
• Cascade of Phase Transitions and Dirac Revivals in Magic Angle Graphene
• Band Structure of ABC-Stacked Graphene Trilayers
• Nearly Flat Chern Bands in Moiré Superlattices
• Electrical switching of magnetic order in an orbital Chern insulator
• Robust fractional quantum Hall states and continuous quantum phase transitions in a half-filled bilayer graphene Landau level
• Interlayer screening effect in graphene multilayers with ABA and ABC stacking
• Phase diagram for the $\nu =0$ quantum Hall state in monolayer graphene
• Electronic phase separation in topological surface states of rhombohedral graphite
• Gate-Tunable Topological Flat Bands in Trilayer Graphene-Boron Nitride Moiré Superlattices
• Accurate tight-binding and continuum models for the $\pi$ bands of bilayer graphene
• Evidence for a Spin Phase Transition at ν=0 in Bilayer Graphene
• Fabrication of graphene nanoribbon by local anodic oxidation lithography using atomic force microscope
• Low density ferromagnetism in biased bilayer graphene
• Anomalous sequence of quantum Hall liquids revealing tunable Lifshitz transition in bilayer graphene
• Observation of Spontaneous Ferromagnetism in a Two-Dimensional Electron System
• Quantitative transport measurements of fractional quantum Hall energy gaps in edgeless graphene devices
• Emergent Dirac gullies and gully-symmetry breaking quantum Hall states in ABA trilayer graphene
• New Dirac points and multiple Landau level crossings in biased trilayer graphene
• High-magnetic-field Tunneling Spectra of ABC-Stacked Trilayer Graphene
• Interplay between lattice-scale physics and the quantum Hall effect in graphene
• Gate Tunable Magnetism and Giant Magnetoresistance in ABC-stacked Few-Layer Graphene

Cited by in corpus (64)

• Superconductivity in rhombohedral trilayer graphene
• Isospin magnetism and spin-triplet superconductivity in Bernal bilayer graphene
• Quantum cascade of new correlated phases in trigonally warped bilayer graphene
• Cascade of isospin phase transitions in Bernal bilayer graphene at zero magnetic field
• Correlated Insulator and Chern Insulators in Pentalayer Rhombohedral Stacked Graphene
• The Quantum Twisting Microscope
• Orbital Multiferroicity in Pentalayer Rhombohedral Graphene
• Signatures of Chiral Superconductivity in Rhombohedral Graphene
• Inter-valley coherent order and isospin fluctuation mediated superconductivity in rhombohedral trilayer graphene
• Unconventional superconductivity in systems with annular Fermi surfaces: Application to rhombohedral trilayer graphene
• Correlated Hofstadter Spectrum and Flavor Phase Diagram in Magic Angle Graphene
• Superconductivity and correlated phases in non-twisted bilayer and trilayer graphene
• Josephson Diode Effect Induced by Valley Polarization in Twisted Bilayer Graphene
• Tunable superconductivity in electron- and hole-doped Bernal bilayer graphene
• Superconductivity from Repulsive Interactions in Rhombohedral Trilayer Graphene: a Kohn-Luttinger-Like Mechanism
• Superconductivity and quantized anomalous Hall in rhombohedral graphene
• Acoustic-phonon-mediated superconductivity in Bernal bilayer graphene
• Bound on resistivity in flat-band materials due to the quantum metric
• Spin and Orbital Metallic Magnetism in Rhombohedral Trilayer Graphene
• Metals, fractional metals, and superconductivity in rhombohedral trilayer graphene
• Superconductivity from electronic interactions and spin-orbit enhancement in bilayer and trilayer graphene
• Local atomic stacking and symmetry in twisted graphene trilayers
• Quantum Metric Induced Phases in Moiré Materials
• Heavy quasiparticles and cascades without symmetry breaking in twisted bilayer graphene
• Multilayer graphenes as a platform for interaction-driven physics and topological superconductivity
• Spin-triplet superconductivity at the onset of isospin order in biased bilayer graphene
• Pairing symmetry of twisted bilayer graphene: a phenomenological synthesis
• Functional Renormalization Group Study of Superconductivity in Rhombohedral Trilayer Graphene
• Competing orders and cascade of degeneracy lifting in doped Bernal bilayer graphene
• Isospin competitions and valley polarized correlated insulators in twisted double bilayer graphene
• Flavor symmetry breaking in spin-orbit coupled bilayer graphene
• Correlated metals and unconventional superconductivity in rhombohedral trilayer graphene: A renormalization group analysis
• Isospin and momentum polarized orders in bilayer graphene
• Acoustic-phonon-mediated superconductivity in moiréless graphene multilayers
• Enhanced superconductivity through virtual tunneling in Bernal bilayer graphene coupled to WSe${}_2$
• Experimental observation of ABCB stacked tetralayer graphene
• Tunable ferromagnetism at non-integer filling of a moiré superlattice
• Engineering Proximity Exchange by Twisting: Reversal of Ferromagnetic and Emergence of Antiferromagnetic Dirac Bands in Graphene/Cr${}_2$Ge${}_2$Te${}_6$
• Intrinsic spin Hall torque in a moire Chern magnet
• Observation of competing, correlated ground states in the flat band of rhombohedral graphite
• Strong manipulation of the valley splitting upon twisting and gating in MoSe${}_2$/CrI${}_3$ and WSe${}_2$/CrI${}_3$ van der Waals heterostructures
• Superconductivity induced by the inter-valley Coulomb scattering in a few layers of graphene
• Superconductivity and spin canting in spin-orbit proximitized rhombohedral trilayer graphene
• Hofstadter states and reentrant charge order in a semiconductor moiré lattice
• Layer-dependent evolution of electronic structures and correlations in rhombohedral multilayer graphene
• TU${}^2$FRG -- a scalable approach for truncated unity functional renormalization group in generic fermionic models
• Direct Visualization of Native Defects in Graphite and Their Effect on the Electronic Properties of Bernal-Stacked Bilayer Graphene
• Quantum Monte Carlo study of superconductivity in rhombohedral trilayer graphene under an electric field
• Relative Stability of Bernal and Rhombohedral Stackings in Trilayer Graphene under Distortions
• Narrow bands, electrostatic interactions and band topology in graphene stacks
• Strong correlations in ABC-stacked trilayer graphene: Moiré is important
• Cascade of transitions in twisted and non-twisted graphene layers within the van Hove scenario
• Layer photovoltaic effect in van der Waals heterostructures
• Half-metal and other fractional metal phases in doped AB bilayer graphene
• Nodal pair density waves from a quarter-metal in crystalline graphene multilayers
• Phonon-limited resistivity of multilayer graphene systems
• Mott correlations in ABC graphene trilayer aligned with hBN
• Fluctuating magnetism and Pomeranchuk effect in multilayer graphene
• Re-entrant Superconductivity Through a Quantum Lifshitz Transition in Twisted Trilayer Graphene
• Chiral Stoner magnetism in Dirac bands
• Gate-induced half-metals in Bernal stacked graphene multilayer
• Deep learning extraction of band structure parameters from density of states: a case study on trilayer graphene
• Quantum Magnetism in Wannier-Obstructed Mott Insulators
• Current-induced re-entrant superconductivity and extreme nonreciprocal superconducting diode effect in valley-polarized systems