Superconductivity Modulated by Carbonization and Hydrogenation in Two-Dimensional MXenes $M_{2}$N ($M$ = Mo, W)
Xin-Zhu Yin1, Hao Wang1, Qiu-Hao Wang1, Na Jiao1*, Mei-Yan Ni1, Meng-Meng Zheng1, Hong-Yan Lu1*, and Ping Zhang1,2*
1School of Physics and Physical Engineering, Qufu Normal University, Qufu 273165, China 2Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Abstract：The superconductivity of two-dimensional (2D) materials has extremely important research significance. To date, superconducting transition temperatures ($T_{\rm c}$) of 2D superconductors are still far from practical applications. Previously, 2D MXene Mo$_2$N has been successfully synthesized [Urbankowski et al.Nanoscale9 17722, (2017)]. We systematically investigate the effects of carbonization and further hydrogenation on the stability, electronic property and superconductivity of 1T- and 2H-$M_{2}$N ($M$ = Mo, W) based on first-principles calculations. The results show that the 1T-$M_{2}$N and 2H-$M_{2}$N ($M$ = Mo, W) are all dynamically and thermodynamically stable after carbonization and further hydrogenation. After carbonization, $T_{\rm c}$'s of 1T-$M_{2}$NC$_{2}$ ($M$ = Mo, W) are all increased, while $T_{\rm c}$'s of 2H-$M_{2}$NC$_{2}$ ($M$ = Mo, W) are all decreased. By further hydrogenation, the $T_{\rm c}$'s of 1T- and 2H-$M_{2}$NC$_{2}$H$_{2}$ are all increased. Among all of these structures, $T_{\rm c}$ of 1T-Mo$_2$NC$_2$H$_2$ is the highest one, reaching 42.7 K, and the corresponding electron-phonon coupling strength $\lambda$ is 2.27. Therefore, hydrogenation is an effective method to modulate $T_{\rm c}$'s of 2D $M_{2}$NC$_{2}$ ($M$ = Mo, W) materials.
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