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The Spin-Orbit Interaction and Topological Vortices in Unconventional Superconductors

Hosseinabadi, Hossein | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52278 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Kargarian, Mehdi
  7. Abstract:
  8. In this work we introduce a new proposal to realize topological superconductivity. In this model we use a ferromagnetic material with high curie temperature like Nickel in proximity to the surface of a three dimensional topological insulator or equivalently Bismuth which has surface states with strong spin-orbit coupling which makes its surface Hamiltonian similar to the surface of a three dimensional topological insulator.The surface electrons of Bismuth are Dirac fermions with strong spin-orbit interaction. The interaction of surface electrons with magnetic fluctuations in the ferromagnet induces an effective attractive electron-electron interaction among surface electrons upon integration out the magnetic degrees of freedom. The spin-orbit interaction makes the superconductivity topologically non-trivial when the system’s Hamiltonian is projected on the states near the fermi surface. The resulting Cooper pairs are chiral and have definite angular momentum. The vortices in this system can host Majorana bound states at their cores which are crucial in the theory of topological quantum computation. The main advantage of this model to other proposals is the relatively high superconducting transition temperature and therefore a larger order parameter and also a smaller fermi energy which results in a larger energy gap between the Majorana zero energy state and other excited bound states in the vortex.Thus, it is easier to distinguish and identify Majorana fermions in this system by the energy resolution of currently available experimental devices
  9. Keywords:
  10. Spin-Orbit Interaction ; Majorana Fermion ; Vortex Flow (Eddy Current) ; Topological Superconductor ; Unconventional Superconductivity

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