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arXiv · 2403.19890

On the Hartree-Fock Ground State Manifold in Magic Angle Twisted Graphene Systems

Kevin D. Stubbs·Simon Becker·Lin Lin
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Abstract

Recent experiments have shown that magic angle twisted bilayer graphene (MATBG) can exhibit correlated insulator behavior at half-filling. Seminal theoretical results towards understanding this phase in MATBG has shown that Hartree-Fock ground states (with a positive charge gap) can be exact many-body ground states of an idealized flat band interacting (FBI) Hamiltonian. We prove that in the absence of spin and valley degrees of freedom, the only Hartree-Fock ground states of the FBI Hamiltonian for MATBG are two ferromagnetic Slater determinants. Incorporating spin and valley degrees of freedom, we provide a complete characterization of the Hartree-Fock ground state manifold, which is generated by a ${\rm U}(4) \times {\rm U}(4)$ hidden symmetry group acting on five elements. We also introduce new tools for ruling out translation symmetry breaking in the Hartree-Fock ground state manifold, which may be of independent interest.

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Kevin D. Stubbs, Simon Becker, Lin Lin. 2024-03-29. On the Hartree-Fock Ground State Manifold in Magic Angle Twisted Graphene Systems. https://arxiv.org/abs/2403.19890

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