Perpendicular electric field drives Chern transitions and layer polarization changes in Hofstadter bands
arXiv:2212.09690 · doi:10.1038/s41467-022-35421-z
Abstract
Moiré superlattices engineer band properties and enable observation of fractal energy spectra of Hofstadter butterfly. Recently, correlated-electron physics hosted by flat bands in small-angle moiré systems has been at the foreground. However, the implications of moiré band topology within the single-particle framework are little explored experimentally. An outstanding problem is understanding the effect of band topology on Hofstadter physics, which does not require electron correlations. Our work experimentally studies Chern state switching in the Hofstadter regime using twisted double bilayer graphene (TDBG), which offers electric field tunable topological bands, unlike twisted bilayer graphene. Here we show that the nontrivial topology reflects in the Hofstadter spectra, in particular, by displaying a cascade of Hofstadter gaps that switch their Chern numbers sequentially while varying the perpendicular electric field. Our experiments together with theoretical calculations suggest a crucial role of charge polarization changing concomitantly with topological transitions in this system. Layer polarization is likely to play an important role in the topological states in few-layer twisted systems. Moreover, our work establishes TDBG as a novel Hofstadter platform with nontrivial magnetoelectric coupling.
4+11=15 figures, 19+20=39 pages
References in corpus (19)
- Flat Bands in Slightly Twisted Bilayer Graphene
- Continuum Model of the Twisted Bilayer
- Strongly Correlated Chern Insulators in Magic-Angle Twisted Bilayer Graphene
- Chern Insulators and Topological Flat-bands in Magic-angle Twisted Bilayer Graphene
- Electrical switching of magnetic order in an orbital Chern insulator
- 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
- Flatbands in twisted double bilayer graphene
- Imaging orbital ferromagnetism in a moiré Chern insulator
- Band structure and topological property of twisted double bilayer graphenes
- Symmetry broken Chern insulators and magic series of Rashba-like Landau level crossings in magic angle bilayer graphene
- Hofstadter Topology: Non-crystalline Topological Materials at High Flux
- Moiré Commensurability and the Quantum Anomalous Hall Effect in Twisted Bilayer Graphene on Hexagonal Boron Nitride
- Landau levels in twisted bilayer graphene and semiclassical orbits
- Isospin competitions and valley polarized correlated insulators in twisted double bilayer graphene
- Hofstadter butterfly and the quantum Hall effect in twisted double bilayer graphenes
- Bulk valley transport and Berry curvature spreading at the edge of flat bands
- Phase diagram and orbital Chern insulator in twisted double bilayer graphene
- Facile deterministic cutting of 2D materials for twistronics using a tapered fibre scalpel
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- Electric-field switchable chirality in rhombohedral graphene Chern insulators stabilized by tungsten diselenide
- Quantum geometric moment encodes stacking order of moiré matter
- Second-Order Conductivity Probes a Cascade of Singularities in a Moiré Superlattice