论文标题
通过有限长度的边缘状态进行量化传输的稳健性：浮雕拓扑与量子旋转和异常霍尔绝缘子的成像电流密度
Robustness of quantized transport through edge states of finite length: Imaging current density in Floquet topological vs. quantum spin and anomalous Hall insulators
论文作者
论文摘要
传统上，拓扑绝缘子（TIS）的理论分析集中在无限的均匀晶体上，其波形的散装和非平凡拓扑，或其边界宿主表面或边缘金属状态的无限线。但是，实验设备包含附着在正常金属（NM）导线上的有限尺寸拓扑区域，这提出了一个问题，即纵向电导的量化程度以及电子从拓扑上琐碎的NM的过渡到边缘状态。对于最近猜想的二维（2D）Floquet Ti而言，这尤其是紧迫的问题，其中电子从时间独立的NM流动进入时间依赖性边缘状态---使用圆形极性光辐照的浮石烯对浮石辐照的最新实验性实现并未表现出量化的longududical longitudinal或Hall电导率。在这里，我们采用电荷保存解决方案来用于辐射的石墨烯纳米苯的浮部 - 北方绿色功能（NEGFS）来计算纵向的两端电导，以及局部电流密度的空间曲线，电子作为电子从NM传播到floquet Ti的电子电流密度。在浮子Ti的情况下，块状和边缘局部电流密度同样有助于总电流，这导致纵向电导率低于预期的量化高原，而边缘空位略微降低。我们提出了两种实验方案，以检测floquet ti内的散装和边缘电流密度的共存：（i）在辐射的石墨烯内部钻纳米孔，将诱导批量电流密度的反向散射，从而将纵向电导量减少$ \ sim \ sim \ sim 28 $％; （ii）使用钻石NV中心通过局部电流密度产生的磁场成像。
The theoretical analysis of topological insulators (TIs) has been traditionally focused on infinite homogeneous crystals with band gap in the bulk and nontrivial topology of their wavefunctions, or infinite wires whose boundaries host surface or edge metallic states. However, experimental devices contain finite-size topological region attached to normal metal (NM) leads, which poses a question about how precise is quantization of longitudinal conductance and how electrons transition from topologically trivial NM leads into the edge states. This is particularly pressing issues for recently conjectured two-dimensional (2D) Floquet TI where electrons flow from time-independent NM leads into time-dependent edge states---the very recent experimental realization of Floquet TI using graphene irradiated by circularly polarized light did not exhibit either quantized longitudinal or Hall conductance. Here we employ charge conserving solution for Floquet-nonequlibrium Green functions (NEGFs) of irradiated graphene nanoribbon to compute longitudinal two-terminal conductance, as well as spatial profiles of local current density as electrons propagate from NM leads into the Floquet TI. In the case of Floquet TI both bulk and edge local current densities contribute equally to total current, which leads to longitudinal conductance below the expected quantized plateau that is slightly reduced by edge vacancies. We propose two experimental schemes to detect coexistence of bulk and edge current densities within Floquet TI: (i) drilling a nanopore in the interior of irradiated region of graphene will induce backscattering of bulk current density, thereby reducing longitudinal conductance by $\sim 28$%; (ii) imaging of magnetic field produced by local current density using diamond NV centers.
