Predicting superconductivity near 70 K in 1166-type boron-carbon clathrates at ambient pressure

The search for a novel superconductor exhibiting a high critical temperature (high ${T}_{c}$) or even near room temperature at an accessible synthetic pressure is a persistent objective for both experimental and theoretical physicists. Here, we conduct a systematic high-throughput structure search on boron-carbon clathrates at ambient pressure and uncover two stable 1166-type superconductors, ${\mathrm{RbYbB}}_{6}{\mathrm{C}}_{6}$ and ${\mathrm{RbBaB}}_{6}{\mathrm{C}}_{6}$, both exhibiting maximum ${T}_{c}\ensuremath{\sim}70$ K. The high-${T}_{c}$ superconductivity in 1166-type superconductors is attributed to two key factors: an enhanced density of states at the Fermi level and the strong B-C covalent framework in boron-carbon clathrates, which enhance the electron-phonon coupling and facilitate superconductivity at temperatures near the boiling point of liquid nitrogen. These results provide a significant advancement in understanding the underlying mechanisms of superconductivity in 1166-type boron-carbon based superconductors and offer valuable avenues for the design and synthesis of advanced high-temperature superconductors at ambient conditions.