Colossal conductivity anisotropy in 3D metallic carbon films

Harnessing the phenomena of quantum coherence and destructive interference, we have successfully engineered and synthesized a three-dimensional (3D) graphene-based film exhibiting remarkable properties, including metallic thermal conductivity (κ ≈ 150 Wm⁻¹K⁻¹) and electrical conductivity (σ ≈ 320 kSm⁻¹) at room temperature. Notably, these films demonstrate colossal transport anisotropies, reaching approximately 10³ for thermal and 10⁵ for electrical conductivity. This places them among the conducting materials with the highest anisotropies known to date, surpassing even the performance of one-dimensional (1D) carbon nanotubes and two-dimensional (2D) materials like h-BN and MoS₂. These films are synthesized by self-assembly and cross-linking of edge-hydrolyzed graphene flakes. The electron transport between flakes is phonon mediated and at low temperatures the films present quantum critical behavior of a metal to Anderson insulator transition. We measure the electron transport properties in a Hall bar geometry and extract the critical exponents as a function of the sample mobility.