Dirac cones and magic angles in the Bistritzer--MacDonald TBG Hamiltonian
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arXiv
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| Main Authors: | , , , , |
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| Format: | Preprint |
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2024
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| _version_ | 1866910518585851904 |
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| author | Becker, Simon Quinn, Solomon Tao, Zhongkai Watson, Alexander Yang, Mengxuan |
| author_facet | Becker, Simon Quinn, Solomon Tao, Zhongkai Watson, Alexander Yang, Mengxuan |
| contents | We demonstrate the generic existence of Dirac cones in the full Bistritzer--MacDonald Hamiltonian for twisted bilayer graphene. Its complementary set, when Dirac cones are absent, is the set of magic angles. We show the stability of magic angles obtained in the chiral limit by demonstrating that the perfectly flat bands transform into quadratic band crossings when perturbing away from the chiral limit. Moreover, using the invariance of Euler number, we show that at magic angles there are more band crossings beyond these quadratic band crossings. This is the first result showing the existence of magic angles for the full Bistritzer--MacDonald Hamiltonian and solves Open Problem No.2 proposed in the recent survey arXiv:2310.20642. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2407_06316 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Dirac cones and magic angles in the Bistritzer--MacDonald TBG Hamiltonian Becker, Simon Quinn, Solomon Tao, Zhongkai Watson, Alexander Yang, Mengxuan Mathematical Physics Mesoscale and Nanoscale Physics Strongly Correlated Electrons Analysis of PDEs Spectral Theory We demonstrate the generic existence of Dirac cones in the full Bistritzer--MacDonald Hamiltonian for twisted bilayer graphene. Its complementary set, when Dirac cones are absent, is the set of magic angles. We show the stability of magic angles obtained in the chiral limit by demonstrating that the perfectly flat bands transform into quadratic band crossings when perturbing away from the chiral limit. Moreover, using the invariance of Euler number, we show that at magic angles there are more band crossings beyond these quadratic band crossings. This is the first result showing the existence of magic angles for the full Bistritzer--MacDonald Hamiltonian and solves Open Problem No.2 proposed in the recent survey arXiv:2310.20642. |
| title | Dirac cones and magic angles in the Bistritzer--MacDonald TBG Hamiltonian |
| topic | Mathematical Physics Mesoscale and Nanoscale Physics Strongly Correlated Electrons Analysis of PDEs Spectral Theory |
| url | https://arxiv.org/abs/2407.06316 |