Topological robustness revealed by real-time bulk and edge studies

Topology provides an important concept for achieving dissipationless states that are key to sustaining unchanged quantum electron properties to remarkable precisions. So far, most understanding of the protection mechanism comes from edge-state studies in light of scattering effects facilitated by disorder fluctuations. However, the available results do not adequately explain the ubiquitously system-dependent and variable robustness levels. This study investigates reconstructive situations where protected dissipationless modes become global instead of restricted to the sample edge. This is realized in the integer quantum Hall effect hosted in a Corbino sample geometry brought to the verge of a breakdown by an in-plane electric field. Detection of the onset of dissipation is made simultaneously in both longitudinal and transverse directions with two independent measurement setups, one along the sample edge and the other across the bulk. The real-time correspondence between results in orthogonal directions indicates dissipationless charge modes that are dynamically reconfigurable on global scales. A breakdown mechanism is revealed as rare local resonances causing backscattering between these reconfigurable dissipationless current paths bridging opposite sample edges. The enhanced protection is beyond the bare disorder effect and is qualitatively explainable by impurity screening arising from electron-electron interaction. These findings help construct a picture of understanding topological protection as the system's "ability" to reconstruct to preserve chirality, which provides insights to explain the discrepancies in the robustness levels and a means for robustness optimization of various topological orders.