Fractional quantum anomalous Hall effect in multilayer graphene

Nature, Journal Year: 2024, Volume and Issue: 626(8000), P. 759 - 764

Published: Feb. 21, 2024

Language: Английский

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Fractional Chern insulators versus nonmagnetic states in twisted bilayer MoTe2

Physical review. B./Physical review. B, Journal Year: 2024, Volume and Issue: 109(4)

Published: Jan. 29, 2024

Fractionally filled Chern bands with strong interactions may give rise to fractional insulator (FCI) states, the zero-field analog of quantum Hall effect. Recent experiments have demonstrated existence FCIs in twisted bilayer ${\mathrm{MoTe}}_{2}$ without external magnetic fields---most robust at $\ensuremath{\nu}=\ensuremath{-}2/3$---as well as insulators (CIs) $\ensuremath{\nu}=\ensuremath{-}1$. Although appearance both these states is theoretically natural an interacting topological system, repeatedly observe nonmagnetic (or weakly magnetic) (lacking FCIs) $\ensuremath{\nu}=\ensuremath{-}1/3$ and $\ensuremath{-}4/3$, a puzzling result, which has not been fully explained. In this paper, we perform Hartree-Fock exact diagonalization calculations test whether standard moir\'e model (greatly varying) parameter values available literature can reproduce nonmagnetic/weakly $\ensuremath{-}4/3$ unison FCI $\ensuremath{\nu}=\ensuremath{-}2/3$ CI state We focus on experimentally relevant twist angles and, crucially, include remote bands. find that parameters proposed Wang et al. [arXiv:2306.02501] nearly capture experimental phenomena $\ensuremath{\nu}=\ensuremath{-}1/3,\ensuremath{-}2/3,\ensuremath{-}1,\ensuremath{-}4/3$ simultaneously, although predicted ground are still mostly larger dielectric constant $\ensuremath{\epsilon}>10$ than typical hexagonal boron nitride (h-BN) substrate $\ensuremath{\epsilon}\ensuremath{\sim}6$ required. Our results show importance identifying competing orders lay groundwork for further study realistic phase diagram.

Language: Английский

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Moiré fractional Chern insulators. I. First-principles calculations and continuum models of twisted bilayer MoTe2

Physical review. B./Physical review. B, Journal Year: 2024, Volume and Issue: 109(20)

Published: May 7, 2024

The researchers here shed new light on the elusive single-particle model of twisted bilayer MoTe${}_{2}$, a material recently highlighted for hosting fractional Chern insulators at zero magnetic field. By leveraging an advanced machine learning method and density functional theory, team meticulously maps out band structure across various twist angles, revealing pivotal inversion refining theoretical landscape. enhancing continuum with higher harmonic terms, they unveil opposite numbers in valence bands key paving way predicting diverse states. This comprehensive analysis lays groundwork accurately pinpointing correlated phases this intriguing material, offering beacon future explorations.

Language: Английский

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A microscopic perspective on moiré materials

Nature Reviews Materials, Journal Year: 2024, Volume and Issue: 9(7), P. 460 - 480

Published: May 31, 2024

Language: Английский

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Anomalous Hall Crystals in Rhombohedral Multilayer Graphene. I. Interaction-Driven Chern Bands and Fractional Quantum Hall States at Zero Magnetic Field

Physical Review Letters, Journal Year: 2024, Volume and Issue: 133(20)

Published: Nov. 12, 2024

Recent experiments on rhombohedral pentalayer graphene with a substrate-induced moiré potential have identified both Chern insulators and fractional quantum Hall states at zero magnetic field. Surprisingly, these are observed in strong displacement fields where the effects of lattice weak, seem to be readily accessed without fine-tuning. To address experimental puzzles, we study model interacting electrons this geometry. Within self-consistent Hartree-Fock (SCHF) calculations, find an isolated band small bandwidth good Exact diagonalization density-matrix renormalization group calculations confirm hosts Remarkably, is stable wide range angles, four through six layers, varying hopping parameters, and-most strikingly-survives SCHF when vanishes. In limit, state spontaneously breaks time-reversal translation symmetry simultaneously, giving topological crystalline that term "anomalous crystal." We argue general mechanism create bands multilayer graphene, opening door studying interplay between electronic topology, fractionalization, spontaneous breaking.

Language: Английский

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Fractional Quantum Anomalous Hall Effect in Rhombohedral Multilayer Graphene in the Moiréless Limit

Physical Review Letters, Journal Year: 2024, Volume and Issue: 133(20)

Published: Nov. 12, 2024

The standard theoretical framework for fractional quantum anomalous Hall (FQAH) effect assumes an isolated flat Chern band in the single particle level. In this Letter, we challenge paradigm FQAH recently observed pentalayer rhombohedrally stacked graphene aligned with hexagonal boron nitride. We show that external moiré superlattice potential is simply a perturbation model continuous translation symmetry. Through Hartree-Fock calculations, find interaction opens sizable remote-band gap, resulting narrow C=1 at filling ν=1. From exact diagonalization identify phases various fillings. However, states also exist calculations without any potential. suggest (QAH) insulator ν=1 should be viewed as interaction-driven topological Wigner crystal QAH effect, which subsequently pinned by small robust period around 10 nm 4-layer, 5-layer, 6-layer, and 7-layer systems. Our work suggests new direction to explore interplay between topology spontaneous formation vanishing limit. propose system generate control both honeycomb triangular potentials through Coulomb from another layer, can stabilize or suppress depending on density of layer.

Language: Английский

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Tunable moiré materials for probing Berry physics and topology

Nature Reviews Materials, Journal Year: 2024, Volume and Issue: 9(7), P. 481 - 498

Published: April 26, 2024

Language: Английский

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Interplay between topology and correlations in the second moiré band of twisted bilayer MoTe2

Nature Physics, Journal Year: 2025, Volume and Issue: unknown

Published: March 20, 2025

Language: Английский

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Higher Landau-Level Analogs and Signatures of Non-Abelian States in Twisted Bilayer MoTe2

Physical Review Letters, Journal Year: 2025, Volume and Issue: 134(7)

Published: Feb. 20, 2025

Recent experimental discovery of fractional Chern insulators at zero magnetic field in moiré superlattices has sparked intense interests bringing Landau level physics to flat bands. In twisted MoTe_{2} bilayers (tMoTe_{2}), recent theoretical and studies have found three consecutive bands twist angle ∼2°. this Letter, we investigate whether higher can be these At angles 2.00° 1.89°, identify four C=1 for the K valley tMoTe_{2}. By constructing Wannier functions directly from density functional theory (DFT) calculations, a six-orbital model is developed describe bands, with orbitals forming honeycomb lattice. Exact diagonalization on top Hartree-Fock calculations are carried out functions. Especially, when second miniband half-filled, signatures non-Abelian states found. Our Wannier-based approach modeling faithful DFT wave serve as benchmarks continuum models. The possibility realizing anyons also opens up new pathway fault-tolerant quantum information processing.

Language: Английский

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Higher Vortexability: Zero-Field Realization of Higher Landau Levels

Physical Review Letters, Journal Year: 2025, Volume and Issue: 134(10)

Published: March 10, 2025

The rise of moiré materials has led to experimental realizations integer and fractional Chern insulators in small or vanishing magnetic fields. At the same time, a set minimal conditions sufficient guarantee an Abelian state flat band were identified, namely, "ideal" "vortexable" quantum geometry. Such vortexable bands share essential features with lowest Landau level (LL), while excluding need for more fine-tuned aspects such as Berry curvature. A natural important generalization is ask if can be extended capture geometry higher levels, particularly first LL (1LL), where non-Abelian states at ν=1/2,2/5 are known competitive. possibility realizing these zero field, perhaps even exotic ones, could become reality we identify structure 1LL bands. In this work, introduce precise definition geometry, along figure merit that measures how closely given approaches 1LL. Periodically strained Bernal graphene shown realize field. locked icon Physics Subject Headings (PhySH)Chern insulatorsFractional Hall effectGeometric & topological phasesLandau levelsQuantum anomalous effectBilayer grapheneTwisted bilayer

Language: Английский

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