Insulating Electronic States Near the Dirac Point Arising from Twisted Stacking and Curvature in 3D Nanoporous Graphene

TL;DR

This study reveals that 3D nanoporous graphene maintains Dirac electronic states similar to monolayer graphene while exhibiting insulating behavior near the Dirac point due to topological defects and curvature effects.

Contribution

It demonstrates the coexistence of Dirac states and insulating behavior in 3D nanoporous graphene, highlighting the role of curvature and topological defects in electronic properties.

Findings

Dirac states persist in 3D-NPG despite curvature and defects.

Insulating behavior near the Dirac point is observed alongside Dirac states.

Raman G-band softening confirms monolayer-like Dirac states.

Abstract

Twist-stacked graphene with a twist angle $\theta$ of $\sim 5^\circ$--$30^\circ$ retains two-dimensional monolayer graphene-like Dirac states near the Dirac point. In three-dimensional nanoporous graphene (3D-NPG), curvature inherently produces twist-stacking and topological defects required to form a porous network. When regions with $\theta \ge 5^\circ$ dominate, Dirac states in individual layers are expected to persist, allowing the Dirac-electron behavior to be tuned through coupling to the 3D curved geometry. However, predicted band gap formation or localized states have remained unobserved. Here we report that 3D-NPG maintains monolayer-like Dirac electronic states while simultaneously exhibiting insulating behavior near the Dirac point. Raman G-band softening confirms these monolayer-like states, and an Arrhenius-type temperature-resistance trend coexisting with weak localization near the Dirac point indicates partially insulating states induced by topological defects. These findings demonstrate that 3D-NPG hosts distinctive Dirac electronic states coupled to 3D curvature, providing a platform for developing new functionalities in 3D graphene-based electronics and energy devices.