Transporte eléctrico en nanoestructuras topológicas
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Casas Barrera, Oscar Eduardo
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Trabajo de grado - Doctorado
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EspañolFecha de publicación
2019-03-13
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En esta tesis se estudian las propiedades electrónicas y de transporte de heteroestructuras conformadas por grafeno o aislantes topológicos en contacto con materiales superconductores (S) y ferromagnéticos (F). Inicialmente se estudia una juntura NINS (N:normal, I:aislante) a base de grafeno con superconductividad inducida de onda d y p, incluyendo simetrías quirales de carácter topológico, encontrándose algunos rasgos que pueden ser identificados en experimentos. También se analizaron las propiedades de junturas ferromagnéticas y superconductoras sobre la superficie de aislantes topológicos 3D, incluyendo una juntura NSN para el desdoblamiento de pares de Cooper. Las interfases FN exhiben el estado quiral del efecto Hall cuántico anómalo, y las interfases FS los modos quirales de Majorana. Finalmente se muestra que es posible obtener una fase topológica superconductora con simetría de inversión temporal (TRITOPS) sobre la superficie de un aislante topológico en contacto con un solo superconductor convencional, si se considera una contribución interparidad en el potencial de pares, y en esta fase el sistema exhibe pares de Kramers de estados de Majorana en sus fronteras.
Abstract: In this thesis, we study the electronic and transport properties of heterostructures based on graphene or topological insulators in contact with superconducting (S) and ferromagnetic (F) materials. Initially, we consider a graphene-based NINS junction (N:Normal, I:insulator,) with d- and p-wave induced superconductivity, including the topological chiral symmetries, finding some features that can be identified in experiments. We also analyzed the properties of ferromagnetic and superconducting junctions on the surface of 3D topological insulators, including a NSN junction for Cooper pair splitting. The FN interfaces exhibit the chiral state of the anomalous quantum Hall effect, and the FS interfaces chiral Majorana modes. Finally, it is shown that it is possible to obtain a time-reversal topological superconducting phase (TRITOPS) on the surface of a topological insulator in contact with a single conventional superconductor, if an interparity pairing is considered, and in this phase the system exhibits Kramers pairs of Majorana states at its boundaries.
Abstract: In this thesis, we study the electronic and transport properties of heterostructures based on graphene or topological insulators in contact with superconducting (S) and ferromagnetic (F) materials. Initially, we consider a graphene-based NINS junction (N:Normal, I:insulator,) with d- and p-wave induced superconductivity, including the topological chiral symmetries, finding some features that can be identified in experiments. We also analyzed the properties of ferromagnetic and superconducting junctions on the surface of 3D topological insulators, including a NSN junction for Cooper pair splitting. The FN interfaces exhibit the chiral state of the anomalous quantum Hall effect, and the FS interfaces chiral Majorana modes. Finally, it is shown that it is possible to obtain a time-reversal topological superconducting phase (TRITOPS) on the surface of a topological insulator in contact with a single conventional superconductor, if an interparity pairing is considered, and in this phase the system exhibits Kramers pairs of Majorana states at its boundaries.
Abstract
Palabras clave
Transporte eléctrico ; Propiedades electrónicas ; Grafeno ; Superconductividad no convencional ; Reflexiones de Andreev ; Aislantes topológicos ; Superconductores topológicos ; Simetría de inversión temporal ; Modos de Majorana ; Electric transport ; Topological superconductors ; Time-reversal symmetry ; Andreev reflections ; Topological isulators ; Graphene ; Unconventional super-conductivity ; Majorana modes ; Electronic properties