Lattice distortions, moiré phonons, and relaxed electronic band structures in magic-angle twisted bilayer graphene
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| Format: | Preprint |
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2023
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| author | Xie, Bo Liu, Jianpeng |
| author_facet | Xie, Bo Liu, Jianpeng |
| contents | In this work, we present a theoretical research on the lattice relaxations, phonon properties, and relaxed electronic structures in magic-angle twisted bilayer graphene (TBG). We construct a continuum elastic model in order to study the lattice dynamics of magic-angle TBG, where both in-plane and out-of-plane lattice displacements are take into account. The fully relaxed lattice structure calculated using such a model is in quantitative agreement with experimental measurements. Furthermore, we investigate the phonon properties in magic-angle TBG using the continuum elastic model, where both the in-plane and out-of-plane phonon modes are included and treated on equal footing. We identify different types of moiré phonons including in-plane sliding modes, soft out-of-plane flexural modes, as well as out-of-plane breathing modes. The latter two types of phonon modes exhibit interesting monopolar, dipolar, quadrupolar, and octupolar-type out-of-plane vibration patterns. Additionally, we explore the impact of the relaxed moiré superlattice structure on the electronic band structures of magic-angle TBG using an effective continuum model, which shows nearly exact agreement with those calculated using a microscopic atomistic tight-binding approach. Our work lays foundation for further studies on the electron-phonon coupling effects and their interplay with $e$-$e$ interactions in magic-angle TBG. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2305_16640 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Lattice distortions, moiré phonons, and relaxed electronic band structures in magic-angle twisted bilayer graphene Xie, Bo Liu, Jianpeng Mesoscale and Nanoscale Physics Strongly Correlated Electrons In this work, we present a theoretical research on the lattice relaxations, phonon properties, and relaxed electronic structures in magic-angle twisted bilayer graphene (TBG). We construct a continuum elastic model in order to study the lattice dynamics of magic-angle TBG, where both in-plane and out-of-plane lattice displacements are take into account. The fully relaxed lattice structure calculated using such a model is in quantitative agreement with experimental measurements. Furthermore, we investigate the phonon properties in magic-angle TBG using the continuum elastic model, where both the in-plane and out-of-plane phonon modes are included and treated on equal footing. We identify different types of moiré phonons including in-plane sliding modes, soft out-of-plane flexural modes, as well as out-of-plane breathing modes. The latter two types of phonon modes exhibit interesting monopolar, dipolar, quadrupolar, and octupolar-type out-of-plane vibration patterns. Additionally, we explore the impact of the relaxed moiré superlattice structure on the electronic band structures of magic-angle TBG using an effective continuum model, which shows nearly exact agreement with those calculated using a microscopic atomistic tight-binding approach. Our work lays foundation for further studies on the electron-phonon coupling effects and their interplay with $e$-$e$ interactions in magic-angle TBG. |
| title | Lattice distortions, moiré phonons, and relaxed electronic band structures in magic-angle twisted bilayer graphene |
| topic | Mesoscale and Nanoscale Physics Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2305.16640 |