论文标题
晶格集体模式来自魔术角扭曲双层石墨烯的连续模型
Lattice Collective Modes from a Continuum Model of Magic-Angle Twisted Bilayer Graphene
论文作者
论文摘要
我们表明，魔法扭曲的双层石墨烯的绝缘状态支持一系列与三角形晶格位点上局部粒子孔激发相对应的集体模式。我们的理论基于魔术角平带的连续模型。当系统在Moiré带填充$ν= -3 $的Moiré带时，我们的计算表明，基态支持七个低能模式，这些模式远低于整个MoiréBrillouin区域的电荷差距，其中之一与Thz光子密切相结合。低能量的集体模式由一个模型忠实地描述了一个本地$ su（8）$ su（8）$的自由度，我们将其确定为旋转，山谷和轨道伪载体的直接乘积。除了自旋和山谷波模式外，集体模式频谱还包括与平面价和传导带轨道之间的过渡相关的低能量内味激子模式。
We show that the insulating states of magic-angle twisted bilayer graphene support a series of collective modes corresponding to local particle-hole excitations on triangular lattice sites. Our theory is based on a continuum model of the magic angle flat bands. When the system is insulating at moiré band filling $ν=-3$, our calculations show that the ground state supports seven low-energy modes that lie well below the charge gap throughout the moiré Brillouin zone, one of which couples strongly to THz photons. The low-energy collective modes are faithfully described by a model with a local $SU(8)$ degree of freedom in each moiré unit cell that we identify as the direct product of spin, valley, and an orbital pseudospin. Apart from spin and valley-wave modes, the collective mode spectrum includes a low-energy intra-flavor exciton mode associated with transitions between flat valence and conduction band orbitals.
