High-Tc 2D ambient BCS superconductors in hydrogenated transition-metal borides

Abstract The discovery of MgB 2 , with T c of 39 K, has inspired intensive studies on various metal (di)-borides to identify other potential conventional high-temperature superconductors. A possible two-dimensional structure of metal borides with the composition M 2 B 2 has also been proposed. Using density functional theory (DFT), we investigated the phase stability and potential high-temperature superconducting properties from mono-hydrogenated transition metal borides (M 2 B 2 H; M = Sc, Y, V, Nb) to fully hydrogenated transition metal borides (M 2 B 2 H 4 ). The mono-hydrogenated transition metal borides behave like a perturbation of M 2 B 2 , with only minor changes in the electronic structure and phonons, and barely becomes superconducting. In contrast, M 2 B 2 H 4 emerges as a highly promising 2D material, exhibiting a calculated T c of up to 69 K and 83 K for Nb 2 B 2 H 4 and V 2 B 2 H 4 , respectively, at ambient pressure.