论文标题
三角形翘曲，卫星狄拉克点和多个野外调谐的拓扑转换，扭曲的双双层石墨烯
Trigonal Warping, Satellite Dirac Points and Multiple Field Tuned Topological Transitions in Twisted Double Bilayer Graphene
论文作者
论文摘要
我们表明，可以通过更换垂直于石墨烯层平面的电场来调整扭曲双重双层石墨烯中低能双层石墨烯中低能带的谷数。由于存在三角形翘曲，因此可以通过在MoiréBrillouin区域的中央迪拉克锥周围形成三个卫星狄拉克点的形成，这两个过渡可以通过-3和+1的变化-3和+1进行解释。卫星锥与中央狄拉克锥具有相反的手性。考虑到导致金属状态的能量频带的重叠，我们根据间接带隙和异常山谷霍尔电导率构建了系统的实验可观察到的相图。我们表明，虽然大多数中间相变为金属，但存在一个狭窄的参数状态，可以看到三个具有不同量化山谷霍尔电导率的绝缘阶段的过渡。我们系统地研究模型参数中变化对系统相图的影响，以揭示粒子孔不对称和三角形翘曲在构造相图中的重要性。我们还研究了层间隧穿的变化对此相图的影响。
We show that the valley Chern number of the low energy band in twisted double bilayer graphene can be tuned through two successive topological transitions, where the direct bandgap closes, by changing the electric field perpendicular to the plane of the graphene layers. The two transitions with Chern number changes of -3 and +1 can be explained by the formation of three satellite Dirac points around the central Dirac cone in the moiré Brillouin zone due to the presence of trigonal warping. The satellite cones have opposite chirality to the central Dirac cone. Considering the overlap of the bands in energy, which lead to metallic states, we construct the experimentally observable phase diagram of the system in terms of the indirect bandgap and the anomalous valley Hall conductivity. We show that while most of the intermediate phase becomes metallic, there is a narrow parameter regime where the transition through three insulating phases with different quantized valley Hall conductivity can be seen. We systematically study the effects of variations in the model parameters on the phase diagram of the system to reveal the importance of particle-hole asymmetry and trigonal warping in constructing the phase diagram. We also study the effect of changes in interlayer tunneling on this phase diagram.
