论文标题
Moiré异质结构中的极性领域理论
Theory of polar domains in moiré heterostructures
论文作者
论文摘要
在扭曲的双层中发现了非常规铁电行为，这促使将Moiré异质结构视为极性材料。然而，对观察到的铁电性的性质和起源的误解表明，需要更好地理解对Moiré异质结构的极性特性的理论理解。在本文中，提出并通过第一原理计算进行了验证，所有Moiré异质结构均表现出平面外的Moiré极性结构域（MPD）结构。在过渡金属二甲基化合物双层中，由于整个Moiré超级晶格的堆叠布置的变化而发生了层间电荷转移，导致局部的平面外偶极矩，MPD的大小和形状由chalcogen原子主导。尽管所有异质结构中的MPD都对Moiré时期敏感，但只有在同性恋者中，他们才能通过平面外电场进行调节。解决了Moiré异质结构中的铁电性的误解，并提出，唯一可以将MPD视为铁电域的情况是通过全球范围瓦斯在同型bilayer中的三分之一单位单元的三分之一。最后，提供了关于Moiré异质结构的极性特性的一般理论讨论。
The discovery of unconventional ferroelectric behavior in twisted bilayers has prompted the consideration of moiré heterostructures as polar materials. However, misconceptions about the nature and origin of the observed ferroelectricity indicate that a better theoretical understanding of the polar properties of moiré heterostructures is needed. In this paper, it is proposed, and verified with first-principles calculations, that all moiré heterostructures exhibit an out-of-plane moiré polar domain (MPD) structure. In transition metal dichalcogenide bilayers, an interlayer charge transfer occurs due to the change in stacking arrangements throughout the moiré superlattice, leading to a local out-of-plane dipole moment, with the magnitude and shape of the MPDs being dominated by the chalcogen atoms. While the MPDs in all heterostructures are sensitive to the moiré period, it is only in the homo-bilayers that they can be tuned with an out-of-plane electric field. The misconceptions about ferroelectricity in moiré heterostructures are addressed, and it is proposed that the only scenario in which the MPDs can be considered ferroelectric domains is via a global van der Waals sliding by one third of a unit cell in a homo-bilayer. Finally, a general theoretical discussion of the polar properties of moiré heterostructures is provided.
