标题： 在准周期和分形环几何结构中实现平坦的电子能带 显示英文标题

标题： Engineering flat electronic bands in quasiperiodic and fractal loop geometries

摘要： 对于一类准一维环状网络，报道了具有平坦、非色散能带，并在不同尺寸的簇上局域化的单电子本征态的精确构造。准周期性的斐波那契和伯克尔分形几何被嵌入到由均匀磁通量穿过的环臂中。我们推导出一种解析方案，以揭示固定在各种原子位点或它们的簇上的局域单粒子态。通过改变磁场，可以微妙地控制局域化的范围以及平坦能带态在能量空间中的位置。此外，我们还表明，适当调节磁场可以使电子在能带中的有效质量出现再进入行为，并在其符号上出现周期性翻转。 显示英文摘要

摘要： Exact construction of one electron eigenstates with flat, non-dispersive bands, and localized over clusters of various sizes is reported for a class of quasi-one dimensional looped networks. Quasiperiodic Fibonacci and Berker fractal geometries are embedded in the arms of the loop threaded by a uniform magnetic flux. We work out an analytical scheme to unravel the localized single particle states pinned at various atomic sites or over clusters of them. The magnetic field is varied to control, in a subtle way, the extent of localization and the location of the flat band states in energy space. In addition to this we show that, an appropriate tuning of the field can lead to a re-entrant behavior of the effective mass of the electron in a band, with a periodic flip in its sign.