低能Stone-Wales石墨烯的本征Ⅲ型Dirac锥的理论预测
Theoretical prediction of a low-energy Stone-Wales graphene with intrinsic type-III Dirac-cone
摘要：
基于第一性原理方法，我们预测了一种新的低能Stone-Wales石墨烯SW 40，它具有Pbam对称的正交晶格，晶胞中有40个碳原子，形成有序的Stone-Wales图案。计算的SW 40的总能量仅比石墨烯高约133 meV，表明其优异的稳定性超过了所有先前提出的石墨烯同素异形体。我们发现SW 40处理固有的III型Dirac-cone（Phys. Rev. Lett.，120，237403，2018），其由局部线性带和局部平带的带交叉形成，这可以导致系统中的高度各向异性的费米子。有趣的是，这种本征III型Dirac-cone可以有效地调整内层应变，它将被转移到II型和I型Dirac-cone拉伸和压缩应变下，分别。最后，我们建立了一个通用的紧束缚模型来理解SW 40中费米能级附近的电子性质。结果表明，利用相邻Stone-Wales缺陷间的$π$ -电子相互作用可以很好地理解第三类Dirac-cone特征.
英文摘要：
Based on first-principles method we predict a new low-energy Stone-Wales graphene SW40, which has an orthorhombic lattice with Pbam symmetry and 40 carbon atoms in its crystalline cell forming well-arranged Stone-Wales patterns. The calculated total energy of SW40 is just about 133 meV higher than that of graphene, indicating its excellent stability exceeds all the previously proposed graphene allotropes. We find that SW40 processes intrinsic Type-III Dirac-cone (Phys. Rev. Lett., 120, 237403, 2018) formed by band-crossing of a local linear-band and a local flat-band, which can result in highly anisotropic Fermions in the system. Interestingly, such intrinsic type-III Dirac-cone can be effectively tuned by inner-layer strains and it will be transferred into Type-II and Type-I Dirac-cones under tensile and compressed strains, respectively. Finally, a general tight-binding model was constructed to understand the electronic properties nearby the Fermi-level in SW40. The results show that type-III Dirac-cone feature can be well understood by the $π$-electron interactions between adjacent Stone-Wales defects.
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