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, ${\mathrm{RbYbB}}_6{C}_6$ and ${\mathrm{RbBaB}}_6{C}_6$, both exhibiting maximum $T_c\sim 70$ 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.