Carrier transport in two-dimensional topological insulator nanoribbons in the presence of vacancy defects
Carrier transport in two-dimensional topological insulator nanoribbons in the presence of vacancy defects
复制标题
DOI：
10.1088/2053-1583/ab0058
复制
发表时间：
2019-04-01
期刊：
影响因子：
5.5
通讯作者：
Vandenberghe, William G.
中科院分区：
文献类型：
--
作者：
Tiwari, Sabyasachi;Van de Put, Maarten L.;Vandenberghe, William G.
利用非平衡态绿色函数方法，研究了载流子在非理想二维拓扑绝缘体（TI）带中的输运。特别地，我们研究了具有六方晶格结构的二维TI带中空位缺陷对载流子输运的影响。为了解释空位缺陷的随机分布，我们提出了一个统计研究不同的缺陷密度随机抽样不同的缺陷配置。我们表明，TI带的拓扑边缘状态是相当强大的对高浓度（高达2%）的缺陷。在非常高的缺陷密度，我们观察到一个增加的边缘间的相互作用，介导的散装区域内的边缘状态的本地化。这种效应导致在非常高的缺陷浓度（>2%）下的边缘状态（否则受到保护）的显著反向散射，从而导致通过TI带的传导损失。我们将讨论如何使用这种相干空位散射我们的优势，为TI为基础的晶体管的发展。我们发现，有一个最佳浓度的空位产生的开-关电流比高达两个数量级。最后，我们研究了自旋轨道耦合对TI带边缘态鲁棒性的重要性，并表明增加自旋轨道耦合可以进一步增加ON-OFF比。
Using the non-equilibrium Green's function formalism, we study carrier transport through imperfect two-dimensional (2D) topological insulator (TI) ribbons. In particular, we investigate the effect of vacancy defects on the carrier transport in 2D TI ribbons with hexagonal lattice structure. To account for the random distribution of the vacancy defects, we present a statistical study of varying defect densities by stochastically sampling different defect configurations. We demonstrate that the topological edge states of TI ribbons are fairly robust against a high concentration (up to 2%) of defects. At very high defect densities, we observe an increased inter-edge interaction, mediated by the localisation of the edge states within the bulk region. This effect causes significant back-scattering of the, otherwise protected, edge-states at very high defect concentrations (>2%), resulting in a loss of conduction through the TI ribbon. We discuss how this coherent vacancy scattering can be used to our advantage for the development of TI-based transistors. We find that there is an optimal concentration of vacancies yielding an ON-OFF current ratio of up to two orders of magnitude. Finally, we investigate the importance of spin-orbit coupling on the robustness of the edge states in the TI ribbon and show that increased spin-orbit coupling could further increase the ON-OFF ratio.