Three-Dimensional Dirac Electrons at the Fermi Energy in Cubic Inverse Perovskites: Ca_3PbO and its Family

TL;DR

This paper investigates the electronic band structure of cubic inverse perovskites Ca_3PbO and related materials, revealing the presence of three-dimensional Dirac electrons at the Fermi energy and proposing design principles for such materials.

Contribution

It provides the first-principles analysis of Dirac electrons in Ca_3PbO family and develops a tight-binding model to explain their origin and design principles.

Findings

Six equivalent Dirac electrons at the Fermi energy on specific Brillouin zone lines

Dirac electrons are three-dimensional and located exactly at the Fermi energy

Proposed design principles for Dirac electrons in related materials

Abstract

The band structure of cubic inverse perovskites, Ca_3PbO 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 Gamma- 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 Ca_3PbO are also studied, and some design principles for the Dirac electrons in this series of materials are proposed.