Electronic transport and quantum spin Hall effect in InAs/GaSb quantum wells

• Ano de defesa: 2022
• Autor(a) principal: Medeiros, Marcos Henrique Lima de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Adatoms; Computational Physics; Efeito Hall de quântico spin; effective model; Exciton; excitons; Formalismo de Landauer; grafeno; Graphene; isolantes topológicos; kp-model; Kwant; Landauer\'s formalism; QSHE; quantum transport; spintronic; Topological Insulator
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/43/43134/tde-12102022-091545/

The challenges inherent to the research of topological insulators in two dimensions based on HgTe/CdTe quantum wells have spurred the search for alternative platforms to study systems exhibiting the quantum Hall effect of spin. In this context, InAs/GaSb semiconductor quantum wells stand out as an alternative. In this work, we focus on the transport properties in InAs/GaSb quantum well systems in the topological regime. Using an effective Hamiltonian obtained from the kp-formalism, it was possible to develop tight-binding models for different heterostructure configurations (double and triple wells) based on the set of sites in the discretized position space. Using this model, it was possible to calculate the transport properties in different InAs/GaSb nanostructures by numerical calculations with the KWANT package. In the case of double InAs/GaSb wells, we show the topological transition and the formation of edge states by setting the value of a perpendicular electric field. In particular, oscillations occur in the energy gap as a function of the field, indicating an experimentally measurable signature of the formation of topological edge states. Moreover, for symmetric GaSb/InAs/GaSb triple-well systems, our results show the formation of circular current patterns when the Fermi energy is at the threshold between the bulk bands and the Dirac cone. Since the formation of these circular current patterns coincides with pronounced conductivity peaks, this phenomenon can be associated with the Fabry-Pérot effect. In addition to the main work, the formation of excitons in dichalcogenide monolayers of transition metals was also studied, as well as the phenomenon known as \\emph{weak localization} in graphene functionalized with the addition of hydrogen atoms, both works resulting from a stay in the group of prof. Jaroslav Fabian at the University of Regensburg.