Ambient-pressure superconductivity above 100 K in hole-doped carbon clathrates with superior hardness
Yu‐Lin Han, Kaiyue Jiang, Bao‐Tian Wang, Ping Zhang, Hong‐Yan Lu
Abstract
To explore phonon-mediated superconductors with critical temperature (${T}_{c}$) exceeding the liquid-nitrogen temperature under ambient pressure, two pure carbon structures ${\mathrm{C}}_{6}$ and ${\mathrm{C}}_{10}$ 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 $s{p}^{3}$-hybridized covalent $\ensuremath{\sigma}$-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 ${\mathrm{C}}_{6}$ and ${\mathrm{C}}_{10}$ 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 ${T}_{c}$ of hole-doped ${\mathrm{C}}_{6}$ and ${\mathrm{C}}_{10}$ clathrates can reach about 43 K and 150 K, respectively. Additionally, pristine ${\mathrm{C}}_{6}$ and ${\mathrm{C}}_{10}$ 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.