Theory of the Dirac Half Metal and Quantum Anomalous Hall Effect in Mn Intercalated Epitaxial Graphene

TL;DR

This paper predicts that Mn intercalated epitaxial graphene on SiC(0001) can become a Dirac half metal and exhibit the quantum anomalous Hall effect, providing a practical route to realize these exotic states.

Contribution

First-principles calculations show Mn intercalation induces a Dirac half metal and QAH state in epitaxial graphene, advancing understanding of material realization of these phenomena.

Findings

Mn intercalation induces Dirac half metal in epitaxial graphene

Orbital-selective symmetry breaking in one spin channel

System naturally transitions into quantum anomalous Hall state

Abstract

The prospect of a Dirac half metal, a material which is characterized by a bandstructure with a gap in one spin channel but a Dirac cone in the other, is of both fundamental interest and a natural candidate for use in spin-polarized current applications. However, while the possibility of such a material has been reported based on model calculations[H. Ishizuka and Y. Motome, Phys. Rev. Lett. 109, 237207 (2012)], it remains unclear what material system might realize such an exotic state. Using first-principles calculations, we show that the experimentally accessible Mn intercalated epitaxial graphene on SiC(0001) transits to a Dirac half metal when the coverage is > 1/3 monolayer. This transition results from an orbital-selective breaking of quasi-2D inversion symmetry, leading to symmetry breaking in a single spin channel which is robust against randomness in the distribution of Mn intercalates. Furthermore, the inclusion of spin-orbit interaction naturally drives the system into the quantum anomalous Hall (QAH) state. Our results thus not only demonstrate the practicality of realizing the Dirac half metal beyond a toy model but also open up a new avenue to the realization of the QAH effect.