Flat bands in twisted bilayer transition metal dichalcogenides
Flat bands in twisted bilayer transition metal dichalcogenides
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DOI：
10.1038/s41567-020-0958-x
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发表时间：
2020-07-06
期刊：
影响因子：
19.6
通讯作者：
LeRoy, Brian J.
中科院分区：
文献类型：
--
作者：
Zhang, Zhiming;Wang, Yimeng;LeRoy, Brian J.
利用扫描隧道谱，在扭曲双层WSe（2）中的平带在0度和60度扭曲角附近都显示出来。材料的晶体结构产生了一个周期性的电势，电子通过该电势移动，从而产生了它的电子能带结构。当二维材料被堆叠时，所得到的莫尔图案引入了附加的周期性，使得层之间的扭转角成为所得到的异质结构的额外自由度。随着这个角度的变化，电子能带结构被修改，导致具有局域态和增强的电子相关性的平坦能带的可能性（1-6）。在过渡金属二硫属化物中，理论上已经预测在约0度和60度的扭转角范围内对于长莫尔波长出现平带（参考文献104）。(4))给出了比魔角扭曲双层石墨烯宽得多的通用性。在这里，我们使用扫描隧道光谱显示了在3度和57.5度扭曲双层WSe（2）样品的电子结构中存在一个平带。我们在平带能量处的波函数的直接空间映射表明，平带的局域化在3度和57.5度是不同的，与第一性原理密度泛函理论计算一致（4）。
Using scanning tunnelling spectroscopy, the flat bands in twisted bilayer WSe(2)are shown near both 0 degrees and 60 degrees twist angles.The crystal structure of a material creates a periodic potential that electrons move through giving rise to its electronic band structure. When two-dimensional materials are stacked, the resulting moire pattern introduces an additional periodicity so that the twist angle between the layers becomes an extra degree of freedom for the resulting heterostructure. As this angle changes, the electronic band structure is modified leading to the possibility of flat bands with localized states and enhanced electronic correlations(1-6). In transition metal dichalcogenides, flat bands have been theoretically predicted to occur for long moire wavelengths over a range of twist angles around 0 degrees and 60 degrees (ref.(4)) giving much wider versatility than magic-angle twisted bilayer graphene. Here, we show the existence of a flat band in the electronic structure of 3 degrees and 57.5 degrees twisted bilayer WSe(2)samples using scanning tunnelling spectroscopy. Our direct spatial mapping of wavefunctions at the flat-band energy show that the localization of the flat bands is different for 3 degrees and 57.5 degrees, in agreement with first-principles density functional theory calculations(4).