Theoretical prediction of structural stability and superconductivity in T-hexagonal molybdenum dihydrides Monolayer

Abstract

The realization of ambient-pressure, high-temperature superconductivity in hydrogen-rich materials remains a major pursuit in condensed-matter physics. While bulk hydrides require extreme pressures to stabilize, two-dimensional (2D) transition-metal hydrides offer a promising alternative to bypass these compression constraints. In this work, we investigate the structural stability, electronic properties, and phonon-mediated superconductivity of a hexagonal molybdenum dihydride (MoH2) monolayer using first-principles calculations. Total-energy evaluations reveal that the octahedral T-phase is energetically more favorable than the previously reported trigonal prismatic H-phase by 0.198 eV, establishing the T-phase as the true ground-state configuration. Consequently, we systematically evaluate the lattice dynamics and superconducting properties of this ground-state T-MoH2 monolayer within the frameworks of density functional perturbation theory (DFPT) and the anisotropic Migdal-Eliashberg formalism. The transition metal-hydrogen vibrational networks induce strong electron-phonon coupling (EPC), yielding an integrated coupling parameter of \lambda = 1.04. Solving the anisotropic Eliashberg equations predicts a conventional superconducting transition temperature (Tc of 14.4K) at ambient pressure, characterized by a moderately gap distribution (\Delta = 2.07-3.01meV at 5.0 K). Our findings highlight the T-MoH2 monolayer as a structurally, mechanically, and thermally stable platform for exploring low-dimensional conventional superconductivity under ambient conditions.