Coexistense of Dirac and Weyl Fermions in Topological Semimetals

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Davari, Elahe | 2019

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Type of Document: M.Sc. Thesis
Language: Farsi
Document No: 52356 (04)
University: Sharif University of Technology
Department: Physics
Advisor(s): Kargarian, Mehdi
Abstract:
Dirac-Weyl semimetals are new topological phases hosting the coexistence of Dirac and Weyl points in momentum space. Due to the different symmetry requirements of Weyl and Dirac semimetals, one may wonder whether these phases can coexist in real materials. Based on first principles calculations the noncentrosymmetric compounds SrHgPb and CaHgSn have band structure with the Dirac-Weyl crossings. In this thesis we introduce four band minimal lattice models which preserve n-fold rotation along z axis and break inversion symmetry. The obtained models use the minimum number of degrees of freedom, spin and orbital, and proper symmetries relevant to real materials yielding a four-band model where Weyl and Dirac cones coexist near the Fermi energy We used this minimal lattice model and calculate the surface states that appear on the surface of Dirac-Weyl semimetal. We showed that the projections of Weyl nodes on the surfaces are connected by Fermi arcs
Keywords:
Weyl Semimetal ; Dirac Semimetal ; Dirac-Weyl Semimetal ; Fermi Arc