Strong Lattice Anharmonicity and Superconductivity in Janus 1T-Phase MoSH

An accurate description of the vibrations of atoms is essential for studying the stability and superconductivity, especially for materials with strong lattice anharmonicity. The recently synthesized Janus MoSH has sparked extensive research interest due to its unique physical structure. However, under the harmonic approximation, the 1T phase exhibits a charge density wave state, which is considered to be lattice dynamically unstable. In this study, we used the stochastic self-consistent harmonic approximation (SSCHA) to investigate the anharmonic lattice dynamics of 1T-MoSH. The results indicate that the 1T phase is stable, revealing the crucial role of lattice anharmonicity in destroying the charge density wave (CDW) state. Furthermore, the ab initio molecular dynamics (AIMD) simulations show the superior thermal stability of the 1T phase compared to that of the 2H phase. Through the study of electronic structure and electron–phonon interaction mechanisms, the electron–phonon coupling (EPC) constant of 1T-MoSH is determined to be 1.68, with the main source of EPC being the interaction between electrons on the Mo atom's out-of-plane dz2 orbital and the vibration of the Mo atom. By solving the anisotropic Migdal–Eliashberg equations, the superconducting transition temperature Tc of 24.43K is obtained, revealing that 1T-MoSH is a phonon-mediated superconductor with a single-gap. Our study lays the foundation for further investigation of the lattice vibration-related properties of MoSH.