arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2006.01398cond-mat.str-el
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拓扑设计的石墨烯纳米带的量子磁性

Quantum magnetism of topologically-designed graphene nanoribbons

Xingchuan Zhu, Huaiming Guo, Shiping Feng

摘要:

基于哈伯德模型,采用精确的数值模拟方法研究了拓扑设计的石墨烯纳米带的量子磁性。我们首先利用密度矩阵重整化群(DMRG)和行列式量子蒙特卡罗(DQMC)方法研究了描述低能拓扑带的双带哈伯德模型。结果表明,自旋关联随距离迅速衰减,当存在自旋破缺项时,局域矩外推到零。结果表明,两带Hubbard链是对称的,这与平均场计算预测的磁转变的临界相互作用相反。然后,我们包括哈伯德相互作用的拓扑设计的GNRs。对于大的相互作用,自旋关联对所有距离保持有限,并且磁序发展。对于弱相互作用,局部矩外推到几乎为零,并从临界相互作用开始迅速增加。估计的临界值比石墨烯中的实际值大得多,并且我们得出实验相关的GNR为100,这与实验结果一致。

英文摘要:

Based on the Hubbard models, quantum magnetism of topologically-designed graphene nanoribbons (GNRs) is studied using exact numerical simulations. We first study a two-band Hubbard model describing the low-energy topological bands using density matrix renormalization group (DMRG) and determinant quantum Monte Carlo (DQMC) methods. It is found the spin correlations decay quickly with the distance, and the local moment is extrapolated to zero in the presence of symmetry-breaking terms. The results show that the two-band Hubbard chain is nonmagnetic, which is in contrast to the mean-field calculation predicting a critical interaction for the magnetic transition. We then include the Hubbard interaction to the topological-designed GNRs. For large interactions, the spin correlations keep finite for all distances, and the magnetic order develops. The local moment is extrapolated to almost zero for weak interactions, and begins to increase rapidly from a critical interaction. The estimated critical value is much larger than the realistic value in graphene, and we conclude the experimentally relevant GNRs is nonmagnetic, which is consistent with the experimental results.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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