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Investigation of Electron Tunneling Spectroscopy at Topological Superconductors Junctions

Azarash, Mohammad | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53673 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Kargarian, Mehdi
  7. Abstract:
  8. In this thesis, we study the tunneling transport at the interface of superconducting states in Bismuth-Nickel bilayer systems . The electron states on the surface of Bismuth are described by Dirac fermions due to strong inversion symmetry breaking near the surface and strong spin-orbit coupling . The magnetic fluctuations of underneath Nickel give rise to an attractive interaction between electron states of Bismuth and formation of superconducting states . The latter states cann't be described by conventional singlet and triplet pairing symmetries due to lack of spin degeneracy in Bismuth . In previous works, it's shown that the superconducting states break the time-reversal symmetry spontaneously, and the condensate is described by chiral d-wave pairing symmetry, in agreement with optical measurements . Our main goal is to study the Andreev bound states at the interface between aforementioned chiral superconducting states . We use the Blonder-Tinkham-Klapwijk (BTK) model to obtain the phase and temperature dependence of the bound states in various geometries of the interface between chiral states . In particular, we found that the supercurrent in the anti-parallel geometry is much larger than the parallel ones . We also argue that our results have some agreements with recent point contact tunneling measurements in Bismuth-Nickel bilayers . Due to observation of zero energy peaks in tunneling conductance spectroscopy, it is probable that the Majorana bound states hosted by the vortices of the superconducting phase of the Bismuth-Nickel bilayer system and the observed zero energy peaks have same origin
  9. Keywords:
  10. Topological Superconductor ; Spin-Orbit Coupling ; Bismuth/Nickle Superconductivity ; Strongly Coupled Quantum Fields Theory ; spontaneously Time-Reversal Symmetry Breaking ; Andreev Bound States

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