Chern Insulators at Integer and Fractional Filling in Moiré Pentalayer Graphene

Physical Review X, Journal Year: 2025, Volume and Issue: 15(1)

Published: Feb. 27, 2025

The advent of moiré platforms for engineered quantum matter has led to discoveries integer and fractional anomalous Hall effects, with predictions correlation-driven topological states based on electron crystallization. Here, we report an array trivial insulators formed in a lattice rhomobohedral pentalayer graphene (R5G). At doping one per unit cell (ν=1), see correlated insulator Chern number that can be tuned between C=0 +1 by electric displacement field. This is accompanied series additional C=+1 originating from fillings the lattice—ν=1/4, 1/3, 2/3—associated formation moiré-driven electronic crystals. ν=2/3 system exhibits effect at zero magnetic field, but further develops hints incipient C=2/3 modest Our results establish R5G as fertile platform studying competition potential intertwining insulators. Published American Physical Society 2025

Language: Английский

Electric Field-Defined Superlattices in Bilayer Graphene: Formation of Topological Bands in Two Dimensions

Materials, Journal Year: 2025, Volume and Issue: 18(7), P. 1521 - 1521

Published: March 28, 2025

An electric field applied to the Bernal-stacked bilayer graphene opens an energy gap; its reversal in some regions creates domain walls and leads appearance of one-dimensional chiral gapless states localized at walls. Here, we investigate structure with superlattice potential defined by external field. The calculations are performed within atomistic π-electron tight-binding approximation. We study two-dimensional superlattices formed arrays electric-field zigzag armchair directions different polarizations. Chiral discretize due transform into minibands gap. As main result, show that can cross Fermi level for This a new kind topological character form Dirac-like cones crossing points. also has application potential: changing polarization close gap change from semiconducting metallic.

Language: Английский

Topologically Protected Flatness in Chiral Moiré Heterostructures

Physical Review X, Journal Year: 2025, Volume and Issue: 15(2)

Published: May 16, 2025

The observation of delicate correlated phases in twisted heterostructures graphene and transition metal dichalcogenides suggests that moiré flat bands are intrinsically resilient against certain types disorder. Here, we investigate the robustness chiral limit Bistritzer-MacDonald model—applicable to both platforms limits—and demonstrate drastic differences between first magic angle higher angles response symmetric disorder arise, for instance, from lattice relaxation. We understand these using a hidden constant motion permits decomposition non-Abelian gauge field induced by interlayer tunnelings into two decoupled Abelian ones. At all angles, resulting effective magnetic splits an anomalous contribution fluctuating part. maps onto zeroth Dirac Landau level, whose flatness withstands any perturbation such as nonuniform fields due topological index theorem—thereby underscoring mechanism band flatness. Only can fully harness this protection its weak field. In amplitude fluctuations largely exceeds contribution, which find results physically meaningless operator extremely large sensitivity microscopic details exponential collapse single-particle gap. Through numerical simulations, further study various identify scattering processes enhanced or suppressed limit. Interestingly, suppression broadening persists away is accentuated isolating single sublattice polarized energy. Our analysis Berry curvature hot spot at top K K′ valence dichalcogenide monolayers essential stability their states. Published American Physical Society 2025

Language: Английский