Unveiling the Superconducting Mechanism and Phase Stability of LaB 2 H 8 under Pressure

Abstract The recent synthesis of the superhydride LaB 2 H 8 , which exhibits a superconducting transition temperature ( T c ) of 106 K at 90 GPa, offers a promising avenue for exploring high-temperature superconductivity. However, the underlying superconducting mechanism remains elusive. Here, we employ first-principles calculations to systematically investigate its electronic structure, lattice dynamics, electron-phonon coupling and molecular orbital features of LaB 2 H 8 . Our analysis reveals that structural stability and metallic conductivity primarily originate from the covalent B-H bonds within the B 2 H 8 units. Furthermore, we observe a pronounced softening of low-frequency phonons at an elevated pressure, which induces strong electron-phonon coupling and serves as the key driving force of superconductivity in this system. This work not only elucidates the superconducting mechanism in LaB 2 H 8 but also highlights the importance of covalent hydrogen-based motifs in designing new high- T c superconductors.