Protected Topological Nodal Ring Semimetal in Graphene

TL;DR

This paper introduces a topological nodal ring semimetal in graphene, featuring a quantized Hall response, robust edge modes, and protected bulk degeneracy, with potential applications in nano-electronics and quantum entanglement.

Contribution

It presents a novel topological phase in graphene characterized by a protected nodal ring and unique electronic properties not previously identified.

Findings

Quantized quantum Hall response in the new phase

Presence of robust one-dimensional chiral edge modes

Protected bulk band degeneracy due to Z2 symmetry

Abstract

Graphene is a two-dimensional Dirac semimetal showing interesting properties as a result of its dispersion relation with both quasiparticles and quasiholes or matter and anti-matter. We introduce a topological nodal ring semimetal in graphene with a quantized quantum Hall response, a robust one-dimensional chiral edge mode and a quadratic Fermi-liquid spectrum for the quasiparticles and quasiholes in the bulk. The bulk band degeneracy at the Fermi energy is protected through a Z2 symmetry related to the two spin polarizations of an electron and a double-orthogonality structure in the sublattice and spin quantum numbers of the two crossing eigenstates. The system may have applications in nano-electronics and in quantum mechanical entanglement applied to band theory.