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arXiv · 2112.00181

Charge order and antiferromagnetism in twisted bilayer graphene from the variational cluster approximation

B. Pahlevanzadeh·P. Sahebsara·D. Sénéchal
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Abstract

We study the possibility of charge order at quarter filling and antiferromagnetism at half-filling in a tight-binding model of magic angle twisted bilayer graphene. We build on the model proposed by Kang and Vafek [Physical Review X 8(3), 031088 (2018)], relevant to a twist angle of $1.30^\circ$, and add on-site and extended density-density interactions. Applying the variational cluster approximation with an exact-diagonalization impurity solver, we find that the system is indeed a correlated (Mott) insulator at fillings $\frac14$, $\frac12$ and $\frac34$. At quarter filling, we check that the most probable charge orders do not arise, for all values of the interaction tested. At half-filling, antiferromagnetism only arises if the local repulsion $U$ is sufficiently large compared to the extended interactions, beyond what is expected from the simplest model of extended interactions.

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B. Pahlevanzadeh, P. Sahebsara, D. Sénéchal. 2021-11-30. Charge order and antiferromagnetism in twisted bilayer graphene from the variational cluster approximation. https://arxiv.org/abs/2112.00181

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