论文标题
拓扑设计的石墨烯纳米纤维的量子磁性
Quantum magnetism of topologically-designed graphene nanoribbons
论文作者
论文摘要
基于哈伯德模型，使用精确的数值模拟研究了拓扑设计的石墨烯纳米纤维（GNR）的量子磁性。我们首先研究了使用密度矩阵重质化组（DMRG）和行列式量子蒙特卡洛（DQMC）方法描述低能拓扑带（DQMC）方法。发现自旋相关性随距离迅速衰减，在存在对称性术语的情况下，局部力矩被外推至零。结果表明，两频哈伯德链是非磁性的，这与预测磁过渡的关键相互作用的平均场计算相反。然后，我们将Hubbard相互作用与拓扑设计的GNR相互作用。对于大型相互作用，自旋相关性可在所有距离内保持有限，并且磁顺序也会发展。对于弱相互作用而言，当地力矩被推断至几乎为零，并因临界相互作用而开始迅速增加。估计的临界值远大于石墨烯中的现实值，我们得出结论与实验相关的GNR是非磁性的，这与实验结果一致。
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.
