Electronic structure of twisted graphene flakes
Electronic structure of twisted graphene flakes
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DOI：
10.1103/physrevb.87.075433
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发表时间：
2013-02-21
影响因子：
3.7
通讯作者：
Pankratov, O.
中科院分区：
文献类型：
--
作者：
Landgraf, W.;Shallcross, S.;Pankratov, O.
我们研究了双层石墨烯薄片的电子结构，其中组成层相互旋转一定的角度θ。所涉及的大系统尺寸（高达10（5）个碳原子）需要结合Lanczos对角化使用紧束缚方法。我们发现，一个单一的莫尔斑点是足够的低能量密度的状态，以类似于密切的周期性类似的这种薄片，石墨烯扭曲双层，这意味着在这个系统中的低能物理被很好地描述为一个“莫尔量子阱”捕获低能石墨烯电子。此外，由单个莫尔晶胞组成的石墨烯扭曲薄片已经导致AA“莫尔斑”上的电子定位，与该莫尔量子阱图片一致。由扭曲石墨烯薄片中的莫尔晶格引起的电子密度波动是显著的，比由悬浮石墨烯的波纹产生的电子密度波动大一个数量级。最后，我们确定的电子性质的存在下的外部磁场中，这样的薄片，找到一个“零模式”的结构和朗道状态，表现出电子电流以及描述为一个位于AA区域的莫尔晶格的环面上的电荷流。DOI：10.1103/PhysRevB.87.075433
We study the electronic structure of bilayer graphene flakes in which the constituent layers are mutually rotated by some angle theta. The large system sizes involved (up to 10(5) carbon atoms) necessitate the use of a tight-binding approach in conjunction with Lanczos diagonalization. We find that a single moire spot is sufficient for the low-energy density of states to resemble closely that of the periodic analog of such flakes, the graphene twist bilayer, implying that the low-energy physics in this system is well described as that of a "moire quantum well" trapping low-energy graphene electrons. Furthermore, a graphene twist flake consisting of a single moire unit cell leads already to electron localization on the AA "moire spot," in agreement with this moire quantum well picture. The electron density fluctuations induced by the moire lattice in twist graphene flakes are significant, being an order of magnitude greater than those generated by the rippling of suspended graphene. Finally, we determine the electronic properties of such flakes in the presence of an external magnetic field, finding a "zero-mode" structure and Landau states that exhibit an electron current well described as a charge flow on a torus situated at the AA regions of the moire lattice. DOI: 10.1103/PhysRevB.87.075433