Symmetry-broken Chern insulators in twisted double bilayer graphene

Abstract

Twisted double bilayer graphene (tDBG) has emerged as an especially rich platform for studying strongly correlated and topological states of matter. The material features moiré bands that can be continuously deformed by both perpendicular displacement field and twist angle. Here, we construct a phase diagram representing of the correlated and topological states as a function of these parameters, based on measurements on over a dozen tDBG devices encompassing the two distinct stacking configurations in which the constituent Bernal bilayer graphene sheets are rotated either slightly away from 0° or 60°. We find a hierarchy of symmetry-broken states that emerge sequentially as the twist angle approaches an apparent optimal value of $\theta \approx$ 1.34°. Among them, we discover a sequence of symmetry-broken Chern insulator (SBCI) states that arise only within a narrow range of twist angles ($\approx$ 1.33° to 1.39°). We observe an associated anomalous Hall effect at zero field in all samples supporting SBCI states, indicating spontaneous time-reversal symmetry breaking and possible moiré unit cell enlargement at zero magnetic field.

arXiv comment42 pages

References in corpus (30)

• Hofstadter's butterfly in moire superlattices: A fractal quantum Hall effect
• Massive Dirac fermions and Hofstadter butterfly in a van der Waals heterostructure
• Cloning of Dirac fermions in graphene superlattices
• Electric Field Tunable Correlated States and Magnetic Phase Transitions in Twisted Bilayer-Bilayer Graphene
• Spin-polarized Correlated Insulator and Superconductor in Twisted Double Bilayer Graphene
• Correlated states in twisted double bilayer graphene
• Strongly Correlated Chern Insulators in Magic-Angle Twisted Bilayer Graphene
• Chern Insulators and Topological Flat-bands in Magic-angle Twisted Bilayer Graphene
• Observation of fractional Chern insulators in a van der Waals heterostructure
• Correlated Insulating States in Twisted Double Bilayer Graphene
• Topological Nematic States and Non-Abelian Lattice Dislocations
• Flavour Hund's Coupling, Correlated Chern Gaps, and Diffusivity in Moiré Flat Bands
• Hofstadter subband ferromagnetism and symmetry broken Chern insulators in twisted bilayer graphene
• Tunable correlation-driven symmetry breaking in twisted double bilayer graphene
• Imaging orbital ferromagnetism in a moiré Chern insulator
• Symmetry broken Chern insulators and magic series of Rashba-like Landau level crossings in magic angle bilayer graphene
• Bloch Model Wavefunctions and Pseudopotentials for All Fractional Chern Insulators
• Imaging Chern mosaic and Berry-curvature magnetism in magic-angle graphene
• Topological charge density waves at half-integer filling of a moiré superlattice
• Correlated electron-hole State in Twisted Double Bilayer Graphene
• Competing correlated states and abundant orbital magnetism in twisted monolayer-bilayer graphene
• Superconductivity in Twisted Double Bilayer Graphene Stabilized by WSe${}_2$
• Visualizing delocalized correlated electronic states in twisted double bilayer graphene
• Spectroscopy of a Tunable Moiré System with a Correlated and Topological Flat Band
• Isospin competitions and valley polarized correlated insulators in twisted double bilayer graphene
• Spontaneous time-reversal symmetry breaking in twisted double bilayer graphene
• Tailoring the band structure of twisted double bilayer graphene with pressure
• Bulk and Edge Properties of Twisted Double-Bilayer Graphene
• Generalizing Quantum Hall Ferromagnetism to Fractional Chern Bands
• Observation of first-order quantum phase transitions and ferromagnetism in twisted double bilayer graphene

Cited by in corpus (8)

• Tunable moiré materials for probing Berry physics and topology
• Topological electronic crystals in twisted bilayer-trilayer graphene
• Helical trilayer graphene: a moiré platform for strongly-interacting topological bands
• Topological flat bands in a family of multilayer graphene moiré lattices
• Vestigial singlet pairing in a fluctuating magnetic triplet superconductor: Applications to graphene moiré systems
• Chern-Textured Exciton Insulators with Valley Spiral Order in Moiré Materials
• Symmetry-based classification of exact flat bands in single and bilayer moiré systems
• Strongly interacting Hofstadter states in magic-angle twisted bilayer graphene