论文标题
Moiré超晶格效应和带状结构的近30度双层石墨烯
Moiré superlattice effects and band structure evolution in near-30-degree twisted bilayer graphene
论文作者
论文摘要
在二维晶体的堆叠中，其晶格常数不匹配和晶体学轴的未对准导致形成Moiré模式。我们表明，Moiré超级晶格效应在扭曲的双层石墨烯（TBLG）中持续存在，曲折时期很大。使用角度分辨的光发射，我们观察到布里鲁因区域大区域的价带拓扑的急剧变化，包括$ m $ $ m $的马鞍点附近以及从狄拉克点上的3 eV。在这个能量范围内，我们解决了几个Moiré迷你班，并检测重建分散体中次要狄拉克点的特征。对于twists $θ> 21.8^{\ circ} $，低能量的微型胶质不是由于锥形抗穿刺而造成的，而是在较小的扭曲角度上，而是由于一个石墨烯层中的moiré散射在另一个石墨烯层中的潜力，从而产生了InterceTalley耦合。我们的工作证明了机制的鲁棒性，这些机制能够通过调整界面扭曲角来对二维晶体堆栈的电子分散群进行工程。它还表明，大角度TBLG托管了不同起源的电子迷你群和Van Hove奇异性，鉴于石墨烯极端掺杂的最新进展，可以通过实验探索。
In stacks of two-dimensional crystals, mismatch of their lattice constants and misalignment of crystallographic axes lead to formation of moiré patterns. We show that moiré superlattice effects persist in twisted bilayer graphene (tBLG) with large twists and short moiré periods. Using angle-resolved photoemission, we observe dramatic changes in valence band topology across large regions of the Brillouin zone, including the vicinity of the saddle point at $M$ and across 3 eV from the Dirac points. In this energy range, we resolve several moiré minibands and detect signatures of secondary Dirac points in the reconstructed dispersions. For twists $θ>21.8^{\circ}$, the low-energy minigaps are not due to cone anti-crossing as is the case at smaller twist angles but rather due to moiré scattering of electrons in one graphene layer on the potential of the other which generates intervalley coupling. Our work demonstrates robustness of mechanisms which enable engineering of electronic dispersions of stacks of two-dimensional crystals by tuning the interface twist angles. It also shows that large-angle tBLG hosts electronic minigaps and van Hove singularities of different origin which, given recent progress in extreme doping of graphene, could be explored experimentally.
