Ambient-pressure superconductivity above 100 K in hole-doped carbon clathrates with superior hardness

Abstract

To explore phonon-mediated superconductors with critical temperature (Tc) exceeding the liquid-nitrogen temperature under ambient pressure, two pure carbon structures C6 and C10 with a carbon-cage-network are designed and their superconductivity is investigated. By shifting the Fermi level by hole doping, we successfully obtain the metallized sp3-hybridized covalent σ-bonding bands, which generally show strong coupling with phonons. Based on first-principles calculations and the Wannier interpolation technique, the lattice dynamics, mechanical properties, electronic structures, and electron-phonon coupling of hole-doped C6 and C10 clathrates are investigated. Both the enlarged density of states at the Fermi level and the softened phonons play significant roles in the enhancement of electron-phonon coupling. By solving the anisotropic Eliashberg equations, we find that the Tc of hole-doped C6 and C10 clathrates can reach about 43 K and 150 K, respectively. Additionally, pristine C6 and C10 clathrates exhibit ultrahigh hardness simultaneously. This study suggests that a carbon-cage-network is another direction to explore materials simultaneously possessing high-temperature superconductivity and ultrahigh hardness.

Source-reported materials — not catalogue approval

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