Band structure and topological properties of twisted double bilayer graphene
Band structure and topological properties of twisted double bilayer graphene
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DOI：
10.1103/physrevb.99.235406
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发表时间：
2019-06-06
影响因子：
3.7
通讯作者：
Koshino, Mikito
中科院分区：
文献类型：
--
作者：
Koshino, Mikito
我们研究了扭曲双双层石墨烯的电子能带结构和拓扑性质，或一对ab堆叠的双层石墨烯相互旋转堆叠。我们考虑了两种不同的排列，AB-AB和AB-BA，它们的相对取向不同。对于每个系统，我们使用连续统哈密顿量计算了能带和谷陈数。结果表明，AB-AB和AB-BA具有相似的能带结构，但对应能带的陈氏数完全不同。特别是在不存在垂直电场的情况下，当费米能处于间隙时，AB-AB系统是一个平凡的绝缘体，而AB-BA系统是一个谷霍尔绝缘体。此外，AB-AB的最低电子带和空穴带被对称保护带接触点纠缠在一起，而它们在AB-BA中是分离的。在这两种情况下，垂直电场立即在电荷中性点打开一个能隙，在那里，由于显著的电子-空穴不对称，电子分支变得比空穴分支窄得多。
We study the electronic band structure and the topological properties of the twisted double bilayer graphene, or a pair of AB-stacked bilayer graphenes rotationally stacked on top of each other. We consider two different arrangements, AB-AB and AB-BA, which differ in the relative orientation. For each system, we calculate the energy band and the valley Chern number using the continuum Hamiltonian. We show that the AB-AB and the AB-BA have similar band structures, while the Chern numbers associated with the corresponding bands are completely different. In the absence of the perpendicular electric field, in particular, the AB-AB system is a trivial insulator when the Fermi energy is in a gap, while the AB-BA is a valley Hall insulator. Also, the lowest electron and hole bands of the AB-AB are entangled by the symmetry protected band touching points, while they are separated in the AB-BA. In both cases, the perpendicular electric field immediately opens an energy gap at the charge neutral point, where the electron branch becomes much narrower than the hole branch, due to the significant electron-hole asymmetry.