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Topological Superconductors at the Interfaces: the Role of the Spatial Symmetry

Ghadimi, Rasoul | 2019

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51919 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Jafari, Akbar; Kargarian, Mehdi
  7. Abstract:
  8. The zero-energy excitations of topological superconductor promising the design of quantum computers have received a great deal of attentions in recent years. But the materialization has remained to be elusive. Our focus in this thesis is on the one- and two-dimensional systems where the necessary ingredients may conspire to realize topological superconductors. In particular, we will focus on the role of reduction of spatial symmetries near the interfaces. We will start with a one-dimensional system at the boundary of a two-dimensional system with particular orientation so that the full translational symmetry is replaced with a quasi-periodic symmetry. We show that the Fibonacci sequence leads to a fractal dimension about ≈ 1.7 for the boundary of the phase diagram of the Kitaev p-wave chain. We then turn our attention to more realistic electron gas confined at the surfaces or interfaces of heterostructures. Here, the inversion symmetry is broken and consequently a strong Rashba spin-orbit coupling emerges. We obtain a complete phase diagram of superconducting states with the possible realization of topological superconductor. Finally, we consider the
    recently proposed chiral topological superconductivity in epitaxial Bi/Ni bilayer system and show that the in-plane Zeeman field and impurities can induce gapless states. Increasing the strength of either disorder and impurities finally close the gap. We dubbed this state as a gapless chiral superconductor
  9. Keywords:
  10. Topological Superconductor ; Unconventional Superconductivity ; Bismuth/Nickle Superconductivity ; Disorder ; Electron Gas ; Fibonacci Anyon ; Spatial Symmetry

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