论文标题
一维平坦晶格中的rkky互动
RKKY interaction in one-dimensional flat-band lattices
论文作者
论文摘要
我们研究了带有平坦带的一维晶格模型中两个经典的磁杂质之间的Ruderman-Kittel-kasuya-Yosida（rkky）相互作用。作为两个代表性的例子，我们在半填充时选择了存根晶格和钻石晶格。我们首先通过数值计算精确的RKKY相互作用，然后将我们的数据与通过不同的分析技术获得的结果进行比较。在我们的两个示例中，我们都发现Rkky相互作用表现出奇特的特征，可以直接追溯到能量谱中平坦带的存在。重要的是，这些特征并未被基于非脱氧扰动理论的常规rkky近似所捕获。取而代之的是，如果平坦和分散频段之间存在能量差距，那么退化的扰动理论可以正确地再现我们的确切结果，而在没有间隙的情况下，必须进行非扰动方法。
We study the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between two classical magnetic impurities in one-dimensional lattice models with flat bands. As two representative examples, we pick the stub lattice and the diamond lattice at half filling. We first calculate the exact RKKY interaction numerically and then compare our data to results obtained via different analytical techniques. In both our examples, we find that the RKKY interaction exhibits peculiar features that can directly be traced back to the presence of a flat band in the energy spectrum. Importantly, these features are not captured by the conventional RKKY approximation based on non-degenerate perturbation theory. Instead, we find that degenerate perturbation theory correctly reproduces our exact results if there is an energy gap between the flat and the dispersive bands, while a non-perturbative approach becomes necessary in the absence of a gap.
