Two-gap superconductivity in a Janus MoSH monolayer

Abstract

Hydrides under ultrahigh pressure, such as H3S and LaH10, can achieve coveted superconducting critical temperatures via the conventional electron-phonon coupling mechanism. In this work, we report first-principles investigation of high-temperature phonon-mediated superconductivity in a two-dimensional metal hydride, namely, the Janus MoSH monolayer. The MoSH sheet is a recently synthesized intermediate in realizing Janus transition metal dichalcogenides by involving stripping the top-layer S of MoS2 with H atoms [X. Wan et al., ACS Nano 15, 20319 (2021); A. Y. Lu et al., Nat. Nanotechnol. 12, 744 (2017)]. We find coupling of electrons from Mo−d orbitals around the Fermi level to ultrahigh frequency H- and S-derived phonons, analogous to superconducting hydrides of H3S and LaH10. This leads to strong coupling two-gap superconductivity with the calculated critical temperature Tc being about 28.58 K at atmosphere pressure. The presence of soft phonon bands from the Mo in-plane vibrations, in cooperation with the electron susceptibility, accounts for the strong electron-phonon coupling of the MoSH monolayer. By further aligning the Fermi level via doping, the Tc can be boosted to 37.31 K, close to the McMillan limit (39 K). Thus, our work points out a real metal hydride for the realization of two-dimensional high-temperature superconductivity at atmosphere pressure and facilitates further studies on new families of Janus transition-metal sulfhydrates.

Source-reported materials — not catalogue approval

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