论文标题
在临界层间距离处合并了四个零点
Merged Four Dirac Points at the Critical Interlayer Distance in Commensurately Twisted Bilayer Graphene: the Origin of the Zero Velocity
论文作者
论文摘要
我们在紧密结合模型中研究了与层间距离的倾斜双层石墨烯，可以通过压力调节。我们发现，在相应的倾斜双层石墨烯中，具有中等旋转角度的旋转角度时，当k点的能隙不可忽略时，当夹层夹具室内套件时，上两个频段内的其他dirac点沿着双层brill urouzone的$γ$ -K-m线移动。由于上两个频段内的四个狄拉克点的合并，k点的速度变为零。在K点处的零速度的这种机制预计将是在环境压力下具有平坦带的魔术角的起源，在环境压力下，上两个频段几乎是退化的，并且可以忽略K处的带隙。
We study the commensurately-tilted bilayer graphene in the tight-binding model with changing the interlayer distance, which can be tuned by pressure. We find that at the commensurately-tilted bilayer graphene with moderate rotating angles, when the energy gap at K point is not negligible, the other Dirac points within the upper two bands move along the $Γ$-K-M line in the bilayer Brillouzone, when the interlayer distance is changed. The velocity at K point becomes zero due to the merging of the four Dirac points within upper two bands. This mechanism of zero velocity at K point is expected to be the origin of the magic angle with flat band at ambient pressure, at which the upper two bands are almost degenerate and the band gap at K can be neglected.
