标题： 通过氢化增强MXenes的超导性 显示英文标题

标题： Enhancing superconductivity in MXenes through hydrogenation

摘要： 二维过渡金属碳化物和氮化物（MXenes）是一类新兴的原子级超薄超导体，其特性极易通过表面功能化进行调控。 在这里，我们基于第一性原理计算结合Eliashberg理论，探索了氢吸附原子在MXenes中增强声子介导超导性的应用。 我们首先证明了氢化钼和钨基MXenes三种不同结构模型的稳定性。 特别是，对于氢化的Mo$_2$N和W$_2$N，获得了超过30 K的临界温度。 揭示了几种导致电子-声子耦合增强的机制，即（i）氢引起的宿主MXene声子谱的变化，（ii）出现基于氢的声子模式，以及（iii）氢向MXene层的电荷转移，增强了费米能级处的态密度。 最后，我们证明氢吸附原子还能够诱导原本非超导的MXenes表现出超导性，例如Nb$_2$C。 显示英文摘要

摘要： Two-dimensional transition metal carbides and nitrides (MXenes) are an emerging class of atomically-thin superconductors, whose characteristics are highly prone to tailoring by surface functionalization. Here we explore the use of hydrogen adatoms to enhance phonon-mediated superconductivity in MXenes, based on first-principles calculations combined with Eliashberg theory. We first demonstrate the stability of three different structural models of hydrogenated Mo- and W-based MXenes. Particularly high critical temperatures of over 30 K are obtained for hydrogenated Mo$_2$N and W$_2$N. Several mechanisms responsible for the enhanced electron-phonon coupling are uncovered, namely (i) hydrogen-induced changes in the phonon spectrum of the host MXene, (ii) emerging hydrogen-based phonon modes, and (iii) charge transfer from hydrogen to the MXene layer, boosting the density of states at the Fermi level. Finally, we demonstrate that hydrogen adatoms are moreover able to induce superconductivity in MXenes that are not superconducting in pristine form, such as Nb$_2$C.