Topological Node-Line Semimetal in Three Dimensional Graphene Networks

TL;DR

This paper predicts a new topological phase in three-dimensional graphene networks, revealing bulk node-line states and associated surface bands, expanding the understanding of topological properties in carbon-based materials.

Contribution

It introduces a topologically non-trivial 3D carbon network with node-line states, a novel finding in the study of graphene-based materials.

Findings

Discovery of bulk node-line states in 3D graphene networks

Formation of flat surface bands ('drumhead' states)

Potential realization of 3D Dirac points in these structures

Abstract

Graphene, a two dimensional (2D) carbon sheet, acquires many of its amazing properties from the Dirac point nature of its electronic structures with negligible spin-orbit coupling. Extending to 3D space, graphene networks with negative curvature, called Mackay-Terrones crystals (MTC), have been proposed and experimentally explored, yet their topological properties remain to be discovered. Based on the first-principle calculations, we report an all-carbon MTC with topologically non-trivial electronic states by exhibiting node-lines in bulk. When the node-lines are projected on to surfaces to form circles, "drumhead" like flat surface bands nestled inside of the circles are formed. The bulk node-line can evolve into 3D Dirac point in the absence of inversion symmetry, which has shown its plausible existence in recent experiments.