论文标题
扭曲双层石墨烯中的激子效应
Excitonic effects in twisted bilayer graphene
论文作者
论文摘要
在目前的工作中，我们考虑了旋转双层式Hubbard模型中扭曲的双层石墨烯（TBLG）中的激子效应。已经考虑了内层和层间库仑相互作用，并且对电子密度施加了半填充条件，都是双层的层。我们计算出激子配对差距参数以及不同扭曲角度和层间库仑相互作用参数不同值的化学潜力。此外，我们在电子带结构中显示了电子扁平带的外观，并由激子效应介导。我们表明，在低相互作用限制下，狄拉克的$ k $点具有两倍的效果，而狄拉克的节点之一稳定，另一个节点是旋转角度变化的位置。在较大的扭曲角度限制下，在布里鲁因区域的$ m $点上出现了两个额外的类似狄拉克的节点。我们在低相互作用的限制下显示了主要Dirac的点$ K $的激发红移效应，而在强烈的互动中，我们还以$ M $ - 点获得了蓝移效果。除了上述效果外，此处评估的理论还可以预测TBLG系统中的金属 - 肺导体转变，以增加层间库仑相互作用参数。
In the present work, we consider the excitonic effects in the twisted bilayer graphene (tBLG) within the rotated bilayer Hubbard model. Both, intralayer and interlayer Coulomb interactions have been considered and the half-filling condition is imposed for the electronic densities is both layers of the bilayer. We calculate the excitonic pairing gap parameter and the chemical potential for different twist angles and different values of the interlayer Coulomb interaction parameter. Furthermore, we show the appearance of the electronic flat bands in the electronic band structure, mediated by the excitonic effects. We show that there is a doubling effect of the Dirac's $K$-point at the low interaction limit and one of Dirac's nodes is stable and the other one changes its position as a function of rotation angle. At the large twist angle limit, there appear two additional Dirac-like nodes at the $M$-point in the Brillouin zone. We show the excitonic red-shift effect of the principal Dirac's point $K$, in the low interaction limit, while, at the strong interactions, we get also the blue-shift effect at the $M$-point. Apart from the mentioned effects, the theory evaluated here predicts a metal-semiconductor transition in the tBLG system when augmenting the interlayer Coulomb interaction parameter.
