Three-Dimensional Dirac Electrons at the Fermi Energy in Cubic Inverse Perovskites: Ca3PbO and Its Family
The band structure of cubic inverse perovskites, Ca3PbO and its family, are investigated with the first-principles method. A close observation of the band structure reveals that six equivalent Dirac electrons with a very small mass exist on the line connecting the Γ- and X-points, and at the symmetrically equivalent points in the Brillouin zone. The discovered Dirac electrons are three-dimensional and remarkably located exactly at the Fermi energy. A tight-binding model describing the low-energy band structure is also constructed and used to discuss the origin of the Dirac electrons in this material. Materials related to Ca3PbO are also studied, and some design principles for the Dirac electrons in this series of materials are proposed.