Wu Long-Hua, Hu Xiao
International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Tsukuba 305-0044, Japan.
Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan.
Sci Rep. 2016 Apr 14;6:24347. doi: 10.1038/srep24347.
Honeycomb lattice can support electronic states exhibiting Dirac energy dispersion, with graphene as the icon. We propose to derive nontrivial topology by grouping six neighboring sites of honeycomb lattice into hexagons and enhancing the inter-hexagon hopping energies over the intra-hexagon ones. We reveal that this manipulation opens a gap in the energy dispersion and drives the system into a topological state. The nontrivial topology is characterized by the index associated with a pseudo time-reversal symmetry emerging from the C6 symmetry of the hopping texture, where the angular momentum of orbitals accommodated on the hexagonal "artificial atoms" behaves as the pseudospin. The size of topological gap is proportional to the hopping-energy difference, which can be larger than typical spin-orbit couplings by orders of magnitude and potentially renders topological electronic transports available at high temperatures.
蜂窝晶格能够支持具有狄拉克能量色散的电子态，其中石墨烯是典型代表。我们提议通过将蜂窝晶格的六个相邻位点组合成六边形，并增强六边形间的跳跃能量使其高于六边形内的跳跃能量，来导出非平凡拓扑结构。我们发现这种操作会在能量色散中打开一个能隙，并驱使系统进入拓扑状态。这种非平凡拓扑结构由与跳跃纹理的C6对称性所产生的赝时间反演对称性相关的指标来表征，其中容纳在六边形“人工原子”上的轨道角动量表现为赝自旋。拓扑能隙的大小与跳跃能量差成正比，该能量差可能比典型的自旋轨道耦合大几个数量级，并有可能使高温下的拓扑电子输运成为可能。
