Abstract

Two-dimensional hydrogenated graphene (HC₆) represents a promising platform for exploring emergent electronic phases. Owing to its high electronic density of states at the Fermi level, HC₆ is expected to support phonon-mediated superconductivity, with a calculated critical temperature (Tc) of 37.4 K in the paramagnetic metallic phase. However, spin-polarized first-principles calculations reveal that HC₆ stabilizes in a ferrimagnetic ground state, which is energetically favored by 0.175 eV per unit cell over the paramagnetic metallic phase. This large energy difference significantly exceeds kBT at room temperature, indicating robust magnetic order. Although the superconducting condensation energy lowers the total energy by 7 meV, the superconducting phase remains metastable. These results highlight the dominant role of magnetism in HC₆ and illustrate how a high electronic density of states can drive competing instabilities in hydrogenated two-dimensional materials, offering design principles for carbon-based magnetic systems.

Abstract

Two-dimensional hydrogenated graphene (HC₆) represents a promising platform for exploring emergent electronic phases. Owing to its high electronic density of states at the Fermi level, HC₆ is expected to support phonon-mediated superconductivity, with a calculated critical temperature (Tc) of 37.4 K in the paramagnetic metallic phase. However, spin-polarized first-principles calculations reveal that HC₆ stabilizes in a ferrimagnetic ground state, which is energetically favored by 0.175 eV per unit cell over the paramagnetic metallic phase. This large energy difference significantly exceeds kBT at room temperature, indicating robust magnetic order. Although the superconducting condensation energy lowers the total energy by 7 meV, the superconducting phase remains metastable. These results highlight the dominant role of magnetism in HC₆ and illustrate how a high electronic density of states can drive competing instabilities in hydrogenated two-dimensional materials, offering design principles for carbon-based magnetic systems.

Abstract

Two-dimensional hydrogenated graphene (HC₆) represents a promising platform for exploring emergent electronic phases. Owing to its high electronic density of states at the Fermi level, HC₆ is expected to support phonon-mediated superconductivity, with a calculated critical temperature (Tc) of 37.4 K in the paramagnetic metallic phase. However, spin-polarized first-principles calculations reveal that HC₆ stabilizes in a ferrimagnetic ground state, which is energetically favored by 0.175 eV per unit cell over the paramagnetic metallic phase. This large energy difference significantly exceeds kBT at room temperature, indicating robust magnetic order. Although the superconducting condensation energy lowers the total energy by 7 meV, the superconducting phase remains metastable. These results highlight the dominant role of magnetism in HC₆ and illustrate how a high electronic density of states can drive competing instabilities in hydrogenated two-dimensional materials, offering design principles for carbon-based magnetic systems.

Abstract

Two-dimensional hydrogenated graphene (HC₆) represents a promising platform for exploring emergent electronic phases. Owing to its high electronic density of states at the Fermi level, HC₆ is expected to support phonon-mediated superconductivity, with a calculated critical temperature (Tc) of 37.4 K in the paramagnetic metallic phase. However, spin-polarized first-principles calculations reveal that HC₆ stabilizes in a ferrimagnetic ground state, which is energetically favored by 0.175 eV per unit cell over the paramagnetic metallic phase. This large energy difference significantly exceeds kBT at room temperature, indicating robust magnetic order. Although the superconducting condensation energy lowers the total energy by 7 meV, the superconducting phase remains metastable. These results highlight the dominant role of magnetism in HC₆ and illustrate how a high electronic density of states can drive competing instabilities in hydrogenated two-dimensional materials, offering design principles for carbon-based magnetic systems.