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| Autori principali: | , , , , |
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| Natura: | Preprint |
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2026
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| Accesso online: | https://arxiv.org/abs/2603.10433 |
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| _version_ | 1866917332787396608 |
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| author | Kim, Raehyun Kim, Woochang Stubbs, Kevin D. Louie, Steven G. Lin, Lin |
| author_facet | Kim, Raehyun Kim, Woochang Stubbs, Kevin D. Louie, Steven G. Lin, Lin |
| contents | Magic angle twisted bilayer graphene (MATBG) hosts narrow moiré bands with meV-scale energy splittings, making its correlated phases sensitive to both material parameters and modeling choices in low-energy downfolding. We develop an ab initio quantum-embedding workflow that derives interacting flat-band Hamiltonians from Kohn-Sham density functional theory (KS-DFT) of a relaxed, unstrained structure. Our model combines constrained random phase approximation (cRPA) screening, controlled double-counting subtraction, and an automated gauge-fixing procedure based on the selected columns of the density matrix (SCDM) that is compatible with symmetry-resolved many-body calculations. Solving the resulting models using Hartree-Fock (HF) and coupled cluster singles and doubles (CCSD), we recover robust insulating Kramers intervalley coherent (KIVC) states at charge neutrality ($ν=0$) and at electron doping ($ν=+2$). The main new physical effect appears on the hole-doped side: at $ν=-2$ we observe a fragile semimetal with a weak $\sqrt{3}\times\sqrt{3}$ Kekulé modulation and enhanced intervalley-scattering peaks in the Fourier-transformed local density of states. Although the underlying KS-DFT band structure is nearly particle-hole symmetric, the effective interacting Hamiltonian exhibits a pronounced particle-hole asymmetry at $ν=\pm 2$ that we trace to momentum-dependent single-particle renormalizations generated by subtraction terms constructed from reference densities consistent with the KS-DFT filling. Our work provides a first-principles route for connecting microscopic electronic structure, screened interactions, subtraction choices, and scanning tunneling microscopy signatures in MATBG. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_10433 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Ab initio quantum embedding description of magic angle twisted bilayer graphene at even-integer fillings Kim, Raehyun Kim, Woochang Stubbs, Kevin D. Louie, Steven G. Lin, Lin Strongly Correlated Electrons Computational Physics Magic angle twisted bilayer graphene (MATBG) hosts narrow moiré bands with meV-scale energy splittings, making its correlated phases sensitive to both material parameters and modeling choices in low-energy downfolding. We develop an ab initio quantum-embedding workflow that derives interacting flat-band Hamiltonians from Kohn-Sham density functional theory (KS-DFT) of a relaxed, unstrained structure. Our model combines constrained random phase approximation (cRPA) screening, controlled double-counting subtraction, and an automated gauge-fixing procedure based on the selected columns of the density matrix (SCDM) that is compatible with symmetry-resolved many-body calculations. Solving the resulting models using Hartree-Fock (HF) and coupled cluster singles and doubles (CCSD), we recover robust insulating Kramers intervalley coherent (KIVC) states at charge neutrality ($ν=0$) and at electron doping ($ν=+2$). The main new physical effect appears on the hole-doped side: at $ν=-2$ we observe a fragile semimetal with a weak $\sqrt{3}\times\sqrt{3}$ Kekulé modulation and enhanced intervalley-scattering peaks in the Fourier-transformed local density of states. Although the underlying KS-DFT band structure is nearly particle-hole symmetric, the effective interacting Hamiltonian exhibits a pronounced particle-hole asymmetry at $ν=\pm 2$ that we trace to momentum-dependent single-particle renormalizations generated by subtraction terms constructed from reference densities consistent with the KS-DFT filling. Our work provides a first-principles route for connecting microscopic electronic structure, screened interactions, subtraction choices, and scanning tunneling microscopy signatures in MATBG. |
| title | Ab initio quantum embedding description of magic angle twisted bilayer graphene at even-integer fillings |
| topic | Strongly Correlated Electrons Computational Physics |
| url | https://arxiv.org/abs/2603.10433 |