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Majorana bound states in superconductor vortex cores

Mendonça, Bruna Shinohara De

Biblioteca Digital de Teses e Dissertações da USP; Universidade de São Paulo; Instituto de Física 2023-05-02

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  • Título:
    Majorana bound states in superconductor vortex cores
  • Autor: Mendonça, Bruna Shinohara De
  • Orientador: Silva, Luis Gregorio Godoy de Vasconcellos Dias da
  • Assuntos: Física Computacional; Física Da Matéria Condensada; Sistema Quântico
  • Notas: Tese (Doutorado)
  • Descrição: Research into the realization of Majorana quasiparticles has been driven by the relevance of quantum computing and topological materials. Initially, efforts were focused on nanowire realization of Majoranas, but experimental limitations and skepticism led to investigations into two-dimensional setups such as superconducting vortices [1][7]. In this study, we explore the potential and constraints of superconducting vortices as hosts of topological quasiparticles. We examine how scalar impurities can cause false-positive signatures of Majoranas in fully trivial superconductivity. Our findings show that scalar impurities can modify the Caroli-de Gennes-Matricon (CdGM) spectrum, resulting in spectral properties similar to Majorana Zero Modes (MZMs). Local scalar perturbations lower the energy of CdGM states and suppress their total Bardeen-Cooper-Schrieffer (BCS) charge, leading to impurity-driven zero energy states that cannot be distinguished from topological MZMs using local spectroscopic techniques. Additionally, extrinsic broadening of the particle-hole symmetric levels results in vanishing non-local transport signals, making it appear that the BCS charge is zero. These findings have implications for experimental works that rely on finite energy CdGM states [8]. We also investigate the potential of hybrid systems of semiconductors and trivial superconductors as substitutes for intrinsic topological superconductivity, which may provide a more robust way of retaining topological character [9], [10]. Whereas the pwave order parameters complex phase places limitations on the number of vortices that can be introduced, the scalar swave order parameter lacks this constraint. This discrepancy is significant because, despite having an equivalent total number of modes, the edge mode is not suitable for braiding. Furthermore, we remark that unequivocally topological zero energy mode in the topological region is not guaranteed for four vortices and is dependent on a suitably large scattering space, even in the approximation of minimal radii.
  • DOI: 10.11606/T.43.2023.tde-25052023-095947
  • Editor: Biblioteca Digital de Teses e Dissertações da USP; Universidade de São Paulo; Instituto de Física
  • Data de criação/publicação: 2023-05-02
  • Formato: Adobe PDF
  • Idioma: Inglês
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