# Electronic and structural properties of 3D Hopf-linked carbon allotrope: Hopfene

## TL;DR

This paper investigates the electronic and structural properties of a novel 3D carbon allotrope called Hopfene, revealing unique topological features and potential for electronic device applications.

## Contribution

It introduces Hopfene, a new topological 3D carbon allotrope, and analyzes its electronic properties using advanced computational methods, highlighting its tunable conductive features.

## Key findings

- Hopfene exhibits distinct electronic properties from 2D graphene.
- Different sheet spacings lead to varying band structures, including semi-metallic and semiconducting behaviors.
- Hopfene's properties suggest potential for Fermi-level control in device applications.

## Abstract

Electronic and structural properties of a 3D carbon allotrope made of Hopf-linked graphenes, which we call a Hopfene - a type of topological crystal, are examined by semi-empirical molecular-orbital and density-functional-theoretical methods, where band-structure analyses reveal very different properties from those of 2D graphenes. Furthermore, the analyses give an interesting finding that, depending on graphene-sheet spacings, Hopfenes exhibit different band features between primary-type Hopfene with a finite minimum sheet spacing and secondary type with its double-sized spacing. The primary type shows semi-metallic nature and the secondary type exhibits semi-metallic or semiconducting nature at different bands and also has flat bands; these conducting features can be utilised by Fermi-level control. A device application of Hopfenes is also provided.