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Optical Conductivity of Fermi Arc States

Hamidi Ravari, Zeinab | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56513 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Jafari, Akbar
  7. Abstract:
  8. Recently, some materials, such as Weyl and Dirac semimetals, have been found in condensed matter physics whose band structure behaves like Weyl fermions of elementary particles near some points of the first Birillouin zone. The Weyl equation that governs these materials, have boundary because they are finite. By applying proper boundary conditions, two-dimensional surface states have been emerged. these states are called fermi arc sates because the surface corresponding to the fermi energy is not a closed surface. Surface states are mixed with bulk states because by getting close to the end of fermi arcs, surface states tend to bulk states con-tinuously. Being able to distinguish between fermi arc states and bulk states experimentally is very important. In the absorption of light by the material, which is known as the optical con-ductivity test, both the bulk states and the fermi arc states are involved. For this reason, three categories contribute to the optical conductivity: bulk to bulk transition, surface surface tran-sition and finally bulk to surface (or vice versa). In previous researches, they have mainly calculated the contribution of fermi states by supposing a two-dimensional effective hamilto-nian in the surface. But this approach have two problems, first, the surface states should de-rived by the boundary condition not from a separate hamiltonian. Second, the fermi arc states have a deep root in the bulk and this depth increases by getting close to the end of the fermi arc. So it is necessary to take into account this relation between bulk and surface states. Green’s function method is a suitable and efficient way for this goal because all property of fermi arc states are included in the appropriate boundary condition. In the previous researches of the current research team, Green’s function was calculated for proper boundary conditions. Besides, the proportion of bulk and surface states and the mixing states of them have been investigated. In this research, we could calculate the density of optical conductivity tensor by considering the transition between fermi arc to fermi arc states. [19]
  9. Keywords:
  10. Green Function ; Fermi Arc ; Weyl Material ; Optical Conductivity ; Dirac Fermion ; Dirac Materials

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