磁掺杂二维拓扑绝缘体中的反常局域化
Anomalous Localization in Magnetically Doped Two-Dimensional Topological Insulators
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中文总结 AI 辅助
研究磁掺杂二维拓扑绝缘体中输运性质，通过数值模拟建立分析框架，预测安德森局域化起始及反常局域化区域，发现其电导亚指数衰减，且输运有通用缩放行为，应用于Mn掺杂HgTe量子阱与实验吻合，为反常局域化现象提供理论基础。
中文摘要 AI 辅助
二维拓扑绝缘体（2DTIs）具有受时间反演对称性拓扑保护的自旋极化边缘态，可抵御非磁性结构无序。然而，与磁性杂质的耦合会破坏这种对称性，导致背散射并破坏完美量子化。虽然孤立稀磁杂质的影响已被充分理解，但存在密集无序磁矩集合时的输运性质仍知之甚少。本文通过大量数值模拟建立了一个分析框架，以捕捉有限浓度磁性杂质的二维拓扑绝缘体边缘输运行为。预测了安德森局域化的起始，并发现了一个反常局域化区域，其电导呈亚指数衰减，缩放关系为$\ln {\cal G} \propto -\sqrt{L}$，其中$L$是系统长度。还证明输运表现出仅由有效杂质浓度决定的通用缩放行为。将模型应用于Mn掺杂的HgTe量子阱，与实验数据吻合良好。这些发现为理解磁掺杂拓扑相中的反常局域化现象提供了理论基础。
英文摘要
Two-dimensional topological insulators (2DTIs) harbor spin-polarized edge states that are topologically protected by time-reversal symmetry against non-magnetic structural disorder. However, coupling to magnetic impurities breaks this symmetry, inducing backscattering and destroying perfect quantization. While the impact of isolated dilute magnetic impurities is well understood, the transport properties in the presence of dense, disordered ensembles of magnetic moments remain poorly understood. In this work, we develop an analytical framework, supported by extensive numerical simulations, that captures the behavior of edge transport in two-dimensional topological insulators (2DTIs) with a finite concentration of magnetic impurities. We predict the onset of Anderson localization and uncover an anomalous localization regime characterized by a sub-exponential decay of the conductance, scaling as $\ln {\cal G} \propto -\sqrt{L}$, where $L$ is the system length. Furthermore, we demonstrate that the transport exhibits a universal scaling behavior governed solely by the effective impurity concentration. Applying our model to Mn-doped HgTe quantum wells, we find excellent agreement with experimental data. These findings provide a theoretical foundation for understanding anomalous localization phenomena in magnetically doped topological phases.
