Department of Physics, Harbin Institute of Technology, Harbin, 150001, P. R. China.
Nanoscale. 2017 Jul 13;9(27):9693-9700. doi: 10.1039/c7nr03432f.
Graphene spirals (GSs), an emerging carbonic nano-material with a Riemann surface, demonstrate extraordinary topological electronic signatures: interlayer coupling similar to van der Waals (vdW) heterojunctions and intralayer coupling within the spiral conformation. Based on the state-of-the-art first-principles technique, the electronic properties of the periphery-modified GSs with geometry deformation are explored under axial strain. For all GSs, there emerges a remarkable phase transition from metal to semiconductor, due to the attenuation of interlayer "σ-bonds" reducing the interlayer tunneling probability for carriers. Analogous to graphene, GSs consist of bipartite sublattices with carbonic sp hybridization as well. Once the balance of the bipartite sublattices is lost, there will emerge intense edge (corner) states, contributed by the p orbitals. In contrast to isolated graphene nanoflakes, GSs realize the continuous spin-polarized edge (corner) state coupling with 1D morphology. However, the spin-polarization is blocked by the robust interlayer "σ-bonds" so that the spintronic transition takes place until this interlayer coupling is broken. More intriguingly, an indirect-direct bandgap transition is observed, revealing excellent optical on-off features. Their tunable properties provide great potential for their application in optoelectronics, spintronics and chemical or biological sensors.
石墨烯螺旋体（GSs）是一种具有黎曼曲面的新兴碳纳米材料，具有非凡的拓扑电子特性：层间耦合类似于范德华（vdW）异质结，层内耦合在螺旋构象内。基于最先进的第一性原理技术，在轴向应变下研究了具有几何变形的外围修饰 GSs 的电子性质。对于所有的 GSs，由于层间“σ键”的衰减降低了载流子的层间隧道概率，因此会出现从金属到半导体的显著相变。与石墨烯类似，GSs 也由具有碳杂化的二分量子晶格组成。一旦失去二分量子晶格的平衡，就会出现由 p 轨道贡献的强烈边缘（角）态。与孤立的石墨烯纳米片不同，GSs 实现了具有 1D 形态的连续自旋极化边缘（角）态耦合。然而，自旋极化被强的层间“σ键”阻断，只有当这种层间耦合被打破时，才会发生自旋电子跃迁。更有趣的是，观察到间接-直接带隙跃迁，显示出优异的光开关特性。它们的可调谐性质为其在光电子学、自旋电子学以及化学或生物传感器中的应用提供了巨大的潜力。
