论文标题
不对称扭曲石墨烯多层中重新归一化的魔法角度
Renormalized Magic Angles in Asymmetric Twisted Graphene Multilayers
论文作者
论文摘要
发现每个层之间具有小相对扭转角的堆叠石墨烯多层，以一系列魔术角托管平坦的频带。我们考虑到层之间的狄拉克点不对称性，尤其是每一层中不同的费米速度对这种现象的影响。通过与介电底物的库仑相互作用，可以通过不平等的费米速度重新构化来引入这样的不对称性。它也以近似方式出现在四边形系统中，其中外扭角足够大，以至于内部两层的堆叠中有主要的Moire周期性。我们在这样的模型中发现，尽管这种不对称，但平坦的带现象仍然存在，并且魔术角通过控制双层系统中的筛选或四边形系统中外层的扭曲角度获得了一定程度的可调性。值得注意的是，我们在模型中发现魔法角度的定量值增加了。
Stacked graphene multilayers with a small relative twist angle between each of the layers have been found to host flat bands at a series of magic angles. We consider the effect that Dirac point asymmetry between the layers, and in particular different Fermi velocities in each layer, may have on this phenomenon. Such asymmetry may be introduced by unequal Fermi velocity renormalizations through Coulomb interactions with a dielectric substrate. It also arises in an approximate way in tetralayer systems, in which the outer twist angles are large enough that there is a dominant moire periodicity from the stacking of the inner two layers. We find in such models that the flat band phenomenon persists in spite of this asymmetry, and that the magic angles acquire a degree of tunability through either controlling the screening in the bilayer system or the twist angles of the outer layers in the tetralayer system. Notably, we find in our models that the quantitative values of the magic angles are increased.
