Kekulé spiral order at all nonzero integer fillings in twisted bilayer graphene

We study magic angle graphene in the presence of both strain and particle-hole symmetry breaking due to non-local inter-layer tunneling. We perform a self-consistent Hartree-Fock study that incorporates these effects alongside realistic interaction and substrate potentials, and explore a comprehensi...

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Veröffentlicht in:arXiv.org 2021-12
Hauptverfasser: Kwan, Yves H, Wagner, Glenn, Soejima, Tomohiro, Zaletel, Michael P, Simon, Steven H, Parameswaran, Siddharth A, Bultinck, Nick
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Sprache:eng
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Zusammenfassung:We study magic angle graphene in the presence of both strain and particle-hole symmetry breaking due to non-local inter-layer tunneling. We perform a self-consistent Hartree-Fock study that incorporates these effects alongside realistic interaction and substrate potentials, and explore a comprehensive set of competing orders including those that break translational symmetry at arbitrary wavevectors. We find that at all non-zero integer fillings very small strains, comparable to those measured in scanning tunneling experiments, stabilize a fundamentally new type of time-reversal symmetric and spatially non-uniform order. This order, which we dub the 'incommensurate Kekulé spiral' (IKS) order, spontaneously breaks both the emergent valley-charge conservation and moiré translation symmetries, but preserves a modified translation symmetry \(\hat{T}'\) -- which simultaneously shifts the spatial coordinates and rotates the \(U(1)\) angle which characterizes the spontaneous inter-valley coherence. We discuss the phenomenological and microscopic properties of this order. We argue that our findings are consistent with all experimental observations reported so far, suggesting a unified explanation of the global phase diagram in terms of the IKS order.
ISSN:2331-8422
DOI:10.48550/arxiv.2105.05857