论文标题

与增强的交换耦合的重掺杂的蜂窝晶格上的电子订单竞争电子订单

Competing electronic orders on a heavily doped honeycomb lattice with enhanced exchange coupling

论文作者

O, Song-Jin, Kim, Yong-Hwan, Pak, Ok-Gyong, Jong, Kum-Hyok, Ri, Chol-Won, Pak, Hak-Chol

论文摘要

通过扭曲双层石墨烯中最近发现相关的绝缘和超导行为的动机,我们使用截断的统一功能性重量化组方法,重新访问石墨烯的蜂窝晶格掺入了范·霍夫奇异性。我们考虑了蜂窝晶格上的扩展哈伯德模型,包括现场和最近的邻居库仑排斥,以及最近的邻居铁磁交换和配对跳跃相互作用。 By varying the strength of the nearest-neighbor exchange coupling and Coulomb repulsion as free parameters, we present rich ground-state phase diagrams which contain the spin-triplet $f$-wave and spin-singlet chiral $d$-wave superconducting phases, the commensurate and incommensurate spin- and charge-density-wave phases, and the ferromagnetic phase.在没有交换耦合的情况下,对于最近的邻居排斥,在范霍夫填充周围就产生了四个公共旋转密度波相,而手性$ d $ - 波超导率则略微出现。令人惊讶的是,在我们的计算中,手性$ d $ d $ - 波超导率强烈压制。我们认为,这种抑制可能是尚未通过实验观察到掺杂石墨烯的手性超导性的原因之一。

Motivated by recent discovery of correlated insulating and superconducting behavior in twisted bilayer graphene, we revisit graphene's honeycomb lattice doped close to the van Hove singularity, using the truncated unity functional renormalization group approach. We consider an extended Hubbard model on the honeycomb lattice including on-site and nearest-neighbor Coulomb repulsions, and nearest-neighbor ferromagnetic exchange and pair hopping interactions. By varying the strength of the nearest-neighbor exchange coupling and Coulomb repulsion as free parameters, we present rich ground-state phase diagrams which contain the spin-triplet $f$-wave and spin-singlet chiral $d$-wave superconducting phases, the commensurate and incommensurate spin- and charge-density-wave phases, and the ferromagnetic phase. In the absence of the exchange coupling and for small value of the nearest-neighbor repulsion, the four-sublattice spin-density-wave phase is generated right around the van Hove filling, while the chiral $d$-wave superconductivity emerges slightly away from it. Surprisingly, the chiral $d$-wave superconductivity is strongly suppressed by weak nearest-neighbor exchange coupling in our calculations. We argue that this suppression might be one of the reasons why the chiral superconductivity proposed for doped graphene has not yet been observed experimentally.

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