Access Type
Open Access Dissertation
Date of Award
January 2024
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Physics and Astronomy
First Advisor
Jian Huang
Abstract
For a long time, phases of matter were interpreted through order parameters based on specific symmetries, with phase transitions involving symmetry breaking. However, the discovery of Integer Quantum Hall Effect (IQHE) with the Hall quantized resistances h/(ne^2) (n is a filling factor) has reshaped our understanding of phases and transitions. The effectis characterized by dissipationless edge states and insulating bulk states. These exotic properties are determined by a nontrivial topological invariant rather than an order parameter, and unchanged in the presence of perturbations. However, when measuring IQHE, there are two variations that require explanation. First, it is precision level of Hall quantized values. Second, the external factors, needed to break the quantum states, varies considerably and is sample-dependent. It tells us that robustness of quantum states is very different. To understand breakdown mechanism, the most way one focus on in recent years is edge studies, in which they explore any backscattering events that could affect the edge states. On the other hand, there are studies about bulk states, but they don’t include edge states. However, these two methods are separate, even though they investigate the same phenomenon. Therefore, they can’t explain the above variations. Motivated by this lack, this study investigates dynamics of topological breakdown including both bulk and edge states, simultaneously. An IQHE hosted in GaAs/AlGaAs heterostructure samples with Corbino geometry is deployed and brought to the breakdown by applying an in-plane electric field between inner and outer edges. A measurement technique is developed to probe the breakdown in both longitudinal and transverse directions at the same time. The results show that there is one-to-one bulk-edge correspondence participating in the breakdown. A global bulk-edge reconstruction model is proposed to explain the variations in robustness in terms of disorder and long-range screening effect due to electron-electron interaction. It turns out that the topological breakdown mechanism is the backscattering between reconstructed dissipationless currents of opposite chirality on opposite edges due to resonant tunneling effect through incompressible sites distributed randomly in the bulk when "edge” states expand into the bulk under voltage bias.
Recommended Citation
Ho, Hoai Anh, "Topological Robustness Revealed By Real-Time Longitudinal And Transverse Studies" (2024). Wayne State University Dissertations. 4021.
https://digitalcommons.wayne.edu/oa_dissertations/4021
