量子霍尔效应的发现奠定了拓扑凝聚态物理领域的基础。霍尔电导令人惊讶的精确量子化，如今已成为量子度量学的基石，由于其拓扑保护特性，对任何合理扰动都表现出稳定性。反之，后者意味着一种信息屏蔽，向观察者隐瞒了任何局部信息。量子霍尔系统中电流的空间分布就是这样一种信息，得益于近期取得的显著进步，如今已可通过实验探测获取。一个古老的问题是，电流最初直观且引人注目的理论图像，即电流沿着样品边缘的狭窄通道流动，是否是物理上正确的描述。
受近期在Chern绝缘体（Bi, Sb）2Te3异质结构中局部成像量化电流的实验启发[Rosen等，Phys. Rev. Lett. 129, 246602 (2022)；Ferguson等，Nat. Mater. 22, 1100–1105 (2023)]，该研究团队从理论上证明了存在一种广义上蜿蜒远离样品边界深入体内部的宽广“边缘态”的可能性。进一步地，研究人员展示了通过改变实验参数，可以连续调节从具有狭窄边缘态的状态到蜿蜒通道的状态，直至电荷传输主要发生在体内部。这解释了实验中观察到的各种特征及其之间的差异。总体而言，这一研究发现强调了拓扑凝聚态物理的稳健性，但同时也揭示了拓扑屏蔽下隐藏的丰富现象学——研究人员相信，其中大部分仍有待发现。
附：英文原文
Title: Meandering conduction channels and the tunable nature of quantized charge transport
Author: Douot, Benoit, Kovrizhin, Dmitry, Moessner, Roderich
Issue&Volume: 2024-9-19
Abstract: The discovery of the quantum Hall effect has established the foundation of the field of topological condensed matter physics. An amazingly accurate quantization of the Hall conductance, now enshrined in quantum metrology, is stable against any reasonable perturbation due to its topological protection. Conversely, the latter implies a form of censorship by concealing any local information from the observer. The spatial distribution of the current in a quantum Hall system is such a piece of information, which, thanks to spectacular recent advances, has now become accessible to experimental probes. It is an old question whether the original and intuitively compelling theoretical picture of the current, flowing in a narrow channel along the sample edge, is the physically correct one. Motivated by recent experiments locally imaging quantized current in a Chern insulator (Bi, Sb)2Te3 heterostructure [Rosen et al., Phys. Rev. Lett. 129, 246602 (2022); Ferguson et al., Nat. Mater. 22, 1100–1105 (2023)], we theoretically demonstrate the possibility of a broad “edge state” generically meandering away from the sample boundary deep into the bulk. Further, we show that by varying experimental parameters one can continuously tune between the regimes with narrow edge states and meandering channels, all the way to the charge transport occurring primarily within the bulk. This accounts for various features observed in, and differing between, experiments. Overall, our findings underscore the robustness of topological condensed matter physics, but also unveil the phenomenological richness, hidden until recently by the topological censorship—most of which, we believe, remains to be discovered.
DOI: 10.1073/pnas.2410703121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2410703121