Theoretical study of disorder and proximity effects in three-dimensional models of topological insulators

• Autores: Kenan Song
• Directores de la Tesis: Stephan Roche (dir. tes.), Pablo Jesús Ordejon Rontome (codir. tes.)
• Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2018
• Idioma: español
• Tribunal Calificador de la Tesis: Xavier Cartoixà Soler (presid.), Félix Casanova Fernández (secret.), Evgueni Vladimirovich Tchoulkov Savkin (voc.)
• Programa de doctorado: Programa de Doctorado en Física por la Universidad Autónoma de Barcelona
• Materias:
  • Física
    • Física del estado sólido
      • Estados electrónicos
    • Física teórica
• Enlaces
  • Tesis en acceso abierto en: TDX
• Resumen

  • This PhD manuscript mainly covers the theoretical study of the electronic properties of Bi2Se3 family topological insulators, in presence of different defects and proximity effects with a graphene layer. All calculations are based on density functional theory (DFT) method, tight binding (TB) and effective continuum models which allow to obtain simultaneously a realistic description of electronic properties of clean materials, but also to explore the impact of defects and disorder on such properties. Regarding the study of disorder, we have particu-larly scrutinized the impact of rotation mismatches inside the quintuple structure and the ef-fect of surface hydrogenation on the properties of ultrathin TI structures. Besides that, the effect of both non-magnetic and magnetic chemical impurities have been investigated using the generic TB Fu-Kane-Mele (FKM) model of three-dimensional TI in the context of gap opening and changes of the spin textures of the surface states. By varying the density of impurities and their magnetic orientation, a series of conclusions could be made on gap features and evolving spin textures of surface states. Finally, the properties of graphene/TI heterostructures have been studied using DFT and a TB model, fitted to the first-principles calculations. The presence of a spin transport anisotropy was found to be a smoking gun of the proximity effect of the TI on the graphene states, a result which has been also discussed in the context of experimental measurements.