Strongly Interacting Phases in Twisted Bilayer Graphene at the Magic Angle
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arXiv
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| Auteurs principaux: | , , , |
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| Format: | Preprint |
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2023
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| _version_ | 1866910621740564480 |
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| author | Adhikari, Khagendra Seo, Kangjun Beach, K. S. D. Uchoa, Bruno |
| author_facet | Adhikari, Khagendra Seo, Kangjun Beach, K. S. D. Uchoa, Bruno |
| contents | Twisted bilayer graphene near the magic angle is known to have a cascade of insulating phases at integer filling factors of the low-energy bands. In this Letter we address the nature of these phases through an unrestricted, large-scale Hartree-Fock calculation on the lattice that self-consistently accounts for all electronic bands. Using numerically unbiased methods, we show that Coulomb interactions produce ferromagnetic insulating states at integer fillings $ν\in[-3,3]$ with maximal spin polarization $M_{\text{FM}}=4-|ν|$. We find that the $ν=0$ state is a pure ferromagnet, whereas all other insulating states are spin-valley polarized. At odd filling factors $|ν|=1,3$ those states have a quantum anomalous Hall effect with Chern number $\mathcal{C}=1$. Except for the $ν=0,-2$ states, all other integer fillings have insulating phases with additional sublattice symmetry breaking and antiferromagnetism in the remote bands. We map the metal-insulator transitions of these phases as a function of the effective dielectric constant. Our results establish the importance of large-scale lattice calculations to faithfully determine the ground states of TBG at integer fillings. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2308_03843 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Strongly Interacting Phases in Twisted Bilayer Graphene at the Magic Angle Adhikari, Khagendra Seo, Kangjun Beach, K. S. D. Uchoa, Bruno Strongly Correlated Electrons Mesoscale and Nanoscale Physics Twisted bilayer graphene near the magic angle is known to have a cascade of insulating phases at integer filling factors of the low-energy bands. In this Letter we address the nature of these phases through an unrestricted, large-scale Hartree-Fock calculation on the lattice that self-consistently accounts for all electronic bands. Using numerically unbiased methods, we show that Coulomb interactions produce ferromagnetic insulating states at integer fillings $ν\in[-3,3]$ with maximal spin polarization $M_{\text{FM}}=4-|ν|$. We find that the $ν=0$ state is a pure ferromagnet, whereas all other insulating states are spin-valley polarized. At odd filling factors $|ν|=1,3$ those states have a quantum anomalous Hall effect with Chern number $\mathcal{C}=1$. Except for the $ν=0,-2$ states, all other integer fillings have insulating phases with additional sublattice symmetry breaking and antiferromagnetism in the remote bands. We map the metal-insulator transitions of these phases as a function of the effective dielectric constant. Our results establish the importance of large-scale lattice calculations to faithfully determine the ground states of TBG at integer fillings. |
| title | Strongly Interacting Phases in Twisted Bilayer Graphene at the Magic Angle |
| topic | Strongly Correlated Electrons Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2308.03843 |