Berry Curvature of Low-Energy Excitons in Rhombohedral Graphene

Abstract

We investigate low energy excitons in rhombohedral pentalayer graphene encapsulated by hexagonal boron nitride (hBN/R5G/hBN), focusing on the regime at the experimental twist angle $\theta =0.77^{\circ }$ and with an applied electric field. We introduce a new low-energy two-band model of rhombohedral graphene that captures the band structure more accurately than previous models while keeping the number of parameters low. Using this model, we show that the centres of the exciton Wannier functions are displaced from the moiré unit cell origin by a quantised amount - they are instead localised at $C_3$-symmetric points on the boundary. We also find that the exciton shift is electrically tunable: by varying the electric field strength, the exciton Wannier centre can be exchanged between inequivalent corners of the moiré unit cell. Our results suggest the possibility of detecting excitonic corner or edge modes, as well as novel excitonic crystal defect responses in hBN/R5G/hBN. Lastly, we find that the excitons in hBN/R5G/hBN inherit excitonic Berry curvature from the underlying electronic bands, enriching their semiclassical transport properties. Our results position rhombohedral graphene as a compelling tunable platform for probing exciton topology in moiré materials.

18 pages, 9 Figures

References in corpus (23)

• Bulk Topological Invariants in Noninteracting Point Group Symmetric Insulators
• Band Structure of ABC-Stacked Graphene Trilayers
• Electronic properties of graphene hexagonal boron nitride moiré superlattice
• The planar thermal Hall conductivity in the Kitaev magnet α-RuCl3
• Anomalous Hall Crystals in Rhombohedral Multilayer Graphene I: Interaction-Driven Chern Bands and Fractional Quantum Hall States at Zero Magnetic Field
• Theory of quantum anomalous Hall phases in pentalayer rhombohedral graphene moiré structures
• Hyperspectral imaging of excitons within a moiré unit-cell with a sub-nanometer electron probe
• Berry Phase Effect on Exciton Transport and Bose Einstein Condensate
• Exciton band topology in spontaneous quantum anomalous Hall insulators: applications to twisted bilayer graphene
• Thermal Hall effects in quantum magnets
• Stability of Anomalous Hall Crystals in multilayer rhombohedral graphene
• Anomalous Hall Crystals in Rhombohedral Multilayer Graphene II: General Mechanism and a Minimal Model
• Topological Zero-Dimensional Defect and Flux States in Three-Dimensional Insulators
• Interacting topological quantum chemistry of Mott atomic limits
• Theory of topological exciton insulators and condensates in flat Chern bands
• From electrons to baby skyrmions in Chern ferromagnets: A topological mechanism for spin-polaron formation in twisted bilayer graphene
• Interacting Topological Quantum Chemistry in 2D: Many-body Real Space Invariants
• Trions in Twisted Bilayer Graphene
• Characterization and classification of interacting (2+1)D topological crystalline insulators with orientation-preserving wallpaper groups
• Interaction-induced crystalline topology of excitons
• Excitonic topology and quantum geometry in organic semiconductors
• Supercell Wannier functions and a faithful low-energy model for Bernal bilayer graphene
• Exciton Berryology