A planar C3Ca2 film: a novel 2p Dirac half metal

Abstract

The exploration of Dirac materials is a great challenge in condensed matter physics and material chemistry. In this paper we present a novel 2D magnetic graphene-like Dirac material with a Honeycomb–Kagome (HK) lattice, named as C₃Ca₂. The ground state of C₃Ca₂ is a half-metal with a 100% spin polarized Dirac cone locating exactly at the Fermi level in the metallic spin channel, and has a large band gap in the insulating spin channel. In particular, C₃Ca₂ has 2p magnetism with the Dirac cones mainly contributed by p_xy orbitals of C atoms, instead of 3d magnetism or p_z dominated Dirac cones in other HK or Kagome materials, and it is robust against spin–orbit coupling and biaxial strains. The mechanism of magnetism could be understood by double exchange between carbon anions, using Ca²⁺ cations as bridges. These outstanding properties of C₃Ca₂ indicate it to be a promising 2D material for applications in spintronics.