Physics and Astronomy Colloquium: Topological protection probed by real-time bulk and edge measureme
This event is in the past.
Date: September 20, 2022
Time: 3:30 p.m. - 5:00 p.m.
Location: STEM Innovation Learning Center (SILC) # 112 | Map
Please note the different time and location: Tuesday Colloquium -- IN PERSON
Speaker: Dr. Jian Huang, Wayne State University
Title: Topological protection probed by real-time bulk and edge measurement.
Quantum properties associated with topology [1, 2] are unchanged in response to a specific range of variations in the system. This range marks topological robustness that, in real systems (such as quantum Hall  and quantum spin Hall  effects), varies substantially and may even break down in the presence of small disturbances. Investigations of effects influencing topological protection have revealed complicated electron behaviors centered around the notion of topological robustness against disorders  (i.e. in graphene ). However, the question of what makes a topological order more or less robust is not sufficiently addressed by separate studies of the edge states and the bulk states alone. In this study, with an integer quantum Hall effect (IQHE)  hosted in a Corbino two-dimensional system brought to the verge of a topological breakdown, simultaneous measurements of the bulk and edge responses are carried out independently to accurately measure both insulating and conducting behaviors. The source of the topological breakdown is identified as back-scatterings between dissipationless current paths of opposite chirality facilitated by local resonant tunneling. It is captured in real-time correspondence with the emergence of edge dissipation and deviation from Hall quantization. The unique “staircase” features characterizing the breakdown prompt a specific global reconstruction. The enhancement of the bulk localization marks an important contribution from electron-electron interaction that enhances topological robustness through impurity screening. The variations in topological robustness are thus understood as a disorder-interaction interplay. The technique is useful for studying bulk-boundary correspondence (BBC) in various topological quantum matters.  M. Z. Hasan and C. L. Kane, Rev. Mod. Phys. 82, 3045 (2010), URL https://link.aps.org/doi/10.1103/RevModPhys.82.3045.
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