Type-II Dirac cone and Dirac cone protected by nonsymmorphic symmetry in carbon-lithium compound (C4Li)

TL;DR

This paper predicts a novel carbon-lithium compound (C4Li) with unique Dirac cones, including a nonsymmorphic symmetry-protected Dirac point and a type-II Dirac cone, revealing potential for advanced topological electronic properties.

Contribution

The study introduces C4Li as a new material exhibiting both nonsymmorphic symmetry-protected and type-II Dirac cones near the Fermi level, expanding topological material possibilities.

Findings

Presence of two Dirac points near the Fermi level.

One Dirac point protected by nonsymmorphic symmetry.

Identification of a type-II Dirac cone with high anisotropy.

Abstract

In this work, we predict a novel band structure for Carbon-Lithium(C4Li) compound using the first-principles method. We show that it exhibits two Dirac points near the Fermi level; one located at W point originating from the nonsymmophic symmetry of the compound, and the other one behaves like a type-II Dirac cone with higher anisotropy along the {\Gamma} to X line. The obtained Fermi surface sheets of the hole-pocket and the electron-pocket near the type-II Dirac cone are separated from each other, and they would touch each other when the Fermi level is doped to cross the type-II Dirac cone. The evolution of Fermi surface with doping is also discussed. The bands crossing from T to W make a line-node at the intersection of kx={\pi} and ky={\pi} mirror planes. The C4Li is a novel material with both nonsymmorphic protected Dirac cone and type-II Dirac cone near the Fermi level which may exhibit exceptional topological property for electronic applications.