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arXiv · 1812.05661

Spin-Orbital Density Wave and a Mott Insulator in a Two-Orbital Hubbard Model on a Honeycomb Lattice

Zheng Zhu·D. N. Sheng·Liang Fu
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Abstract

Inspired by recent discovery of correlated insulating states in twisted bilayer graphene (TBG), we study a two-orbital Hubbard model on the honeycomb lattice with two electrons per unit cell. Based on the real-space density matrix renormalization group (DMRG) simulation, we identify a metal-insulator transition around $U_c/t=2.5\sim3$. In the vicinity of $U_c$, we find strong spin/orbital density wave fluctuations at commensurate wavevectors, accompanied by weaker incommensurate charge density wave (CDW) fluctuations. The spin/orbital density wave fluctuations are enhanced with increasing system sizes, suggesting the possible emergence of long-range order in the two dimensional limit. At larger $U$, our calculations indicate a possible nonmagnetic Mott insulator phase without spin or orbital polarization. Our findings offer new insights into correlated electron phenomena in twisted bilayer graphene and other multi-orbital honeycomb materials.

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Zheng Zhu, D. N. Sheng, Liang Fu. 2018-12-13. Spin-Orbital Density Wave and a Mott Insulator in a Two-Orbital Hubbard Model on a Honeycomb Lattice. https://doi.org/10.1103/physrevlett.123.087602

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