Spontaneous Valley Spirals in Magnetically Encapsulated Twisted Bilayer Graphene
- 4 February 2021
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 126 (5), 056803
- https://doi.org/10.1103/physrevlett.126.056803
Abstract
Van der Waals heterostructures provide a rich platform for emergent physics due to their tunable hybridization of layers, orbitals, and spin. Here, we find that twisted bilayer graphene stacked between antialigned ferromagnetic insulators can feature flat electronic bands due to the interplay between twist, exchange proximity, and spin–orbit coupling. These flat bands are nearly degenerate in valley only and are effectively described by a triangular superlattice model. At half filling, we find that interactions induce spontaneous valley correlations that favor spiral order and derive a low-energy valley-Heisenberg model with symmetric and antisymmetric exchange couplings. We also show how electric interlayer bias broadens the bands and tunes these couplings. Our results put forward magnetic van der Waals heterostructures as a platform to explore valley-correlated states.Keywords
Funding Information
- Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
- National Center of Competence in Research Quantum Science and Technology
- Academy of Finland
This publication has 95 references indexed in Scilit:
- Superconductivity in metallic twisted bilayer graphene stabilized by WSe2Nature, 2020
- Tunable correlated states and spin-polarized phases in twisted bilayer–bilayer grapheneNature, 2020
- Intrinsic quantized anomalous Hall effect in a moiré heterostructureScience, 2020
- Strange Metal in Magic-Angle Graphene with near Planckian DissipationPhysical Review Letters, 2020
- Superconductors, orbital magnets and correlated states in magic-angle bilayer grapheneNature, 2019
- Tuning superconductivity in twisted bilayer grapheneScience, 2019
- Correlated insulator behaviour at half-filling in magic-angle graphene superlatticesNature, 2018
- Unconventional superconductivity in magic-angle graphene superlatticesNature, 2018
- Helical edge states and fractional quantum Hall effect in a graphene electron–hole bilayerNature Nanotechnology, 2016
- SU(4) Kondo Effect in Carbon NanotubesPhysical Review Letters, 2005