Dirac Fermions in Tetragonal Fe2Ge.

Density functional theory is employed to investigate the electronic band structure of tetragonal Fe 2 Ge. The Dirac cone formation is identified in the bulk electronic configuration of Fe 2 Ge near the Fermi energy level, rather than in the surface states as anticipated. The analysis of Dirac bands suggests that tetragonal Fe 2 Ge can be considered as topological crystalline insulator as suggested by Liang Fu et al. in Phys. Rev. B 76, 045302. The Dirac point exhibits quadratic degeneracy at the high symmetry point 'X' for spin-up channel and at 'M' for spin-down channel in the tetragonal Brillouin zone. The effect of lattice strain and spin-orbit coupling on the energy gap opening at the Dirac point as well as the dependency of the exchange-correlation functional are discussed. These current studies will add a new family of alloys to the topological phase in the band insulators. [ABSTRACT FROM AUTHOR]