论文标题
扭曲双层石墨烯的绝缘和不连贯金属状态中的电荷和自旋相关
Charge and spin correlations in insulating and incoherent metal states of twisted bilayer graphene
论文作者
论文摘要
我们在最近引入的两次公共系统的扩展动力学平均场理论（E-DMFT）的制定中研究了带有填充物的扭曲双层石墨烯的电子，电荷和磁性。我们使用以前获得的状态之间获得的跳跃参数，该状态由Wannier函数描述，以AB和BA堆叠的晶格点为中心，以及在CRPA分析中获得的远距离库仑相互作用。我们表明，AB和BA最近的邻居点之间的自旋交换对引入这些斑点之间的电荷和自旋相关至关重要。对此交换的说明可以在同一山谷中获得优选的电子浓度，并且AB和BA斑点中电子平行对准的趋势与强耦合分析的较早结果一致，表明SU（2）$ \ times $ \ times $ su（2）出现的新兴自旋 - valley对称性。当地光谱功能显示在填充物上几乎差的状态$ n = 2,4,6 $，而其他填充物的金属状态不一致。我们发现，在这两种情况下，当地电子状态的寿命相当长。同时，在梯子近似中获得的非本地电荷和自旋敏感性在不一致的波矢量上达到峰值，这意味着上述讨论的有序趋势的特征是以不相差的模式来表征。
We study electronic, charge, and magnetic properties of twisted bilayer graphene with fillings $2\leq n\leq 6$ per moire unit cell within the recently introduced formulation of extended dynamical mean-field theory (E-DMFT) for two-sublattice systems. We use previously obtained hopping parameters between the states, described by Wannier functions, centered at the lattice spots of AB and BA stacking, and the long-range Coulomb interaction, obtained within cRPA analysis. We show that account of spin exchange between AB and BA nearest neighbour spots is crucial to introduce charge and spin correlations between these spots. Account of this exchange yields preferable concentration of electrons in the same valley, with the tendency of parallel spin alignment of electrons in AB and BA spots, in agreement with earlier results of the strong coupling analysis, suggested SU(2)$\times$SU(2) emergent spin-valley symmetry. The local spectral functions show almost gapped state at the fillings $n=2,4,6$, and incoherent metal state for the other fillings. We find that in both cases the local states of electrons have rather long lifetime. At the same time, the non-local charge- and spin susceptibilities, obtained within the ladder approximation, are peaked at incommensurate wave vectors, which implies that the above discussed ordering tendencies are characterised by an incommensurate pattern.
