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arXiv 1008.3256cond-mat.dis-nn
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紧束缚平带模型中的Anderson局域化

Anderson localisation in tight-binding models with flat bands

J. T. Chalker, T. S. Pickles, Pragya Shukla

摘要:

研究了一类特殊紧束缚模型中弱无序对本征态的影响。这类模型在周期晶格上有短程跳跃;它们的定义特征是干净的系统有一些在布里渊区没有色散的能带。我们表明,从这些平坦的带中得到的状态一般是关键的弱无序的存在下,既不是安德森本地化,也没有空间扩展。此外,我们建立了一个映射之间的本地化问题和随机阻抗网络,以前的工作也建议是至关重要的谐振之一。我们的结论说明了使用数值结果的二维晶格,被称为正方形晶格与交叉或平面烧绿石晶格。

英文摘要:

We consider the effect of weak disorder on eigenstates in a special class of tight-binding models. Models in this class have short-range hopping on periodic lattices; their defining feature is that the clean systems have some energy bands that are dispersionless throughout the Brillouin zone. We show that states derived from these flat bands are generically critical in the presence of weak disorder, being neither Anderson localised nor spatially extended. Further, we establish a mapping between this localisation problem and the one of resonances in random impedance networks, which previous work has suggested are also critical. Our conclusions are illustrated using numerical results for a two-dimensional lattice, known as the square lattice with crossings or the planar pyrochlore lattice.

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