Unveiling the superconducting mechanism and phase stability of LaB₂H₈ under pressure

The recent synthesis of the superhydride LaB₂H₈, 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 the electronic structure, lattice dynamics, electron–phonon coupling, and molecular-orbital features of LaB₂H₈. Our analysis reveals that the structural stability and metallic conductivity primarily originate from the covalent B–H bonds within the B₂H₈ units. Furthermore, we observe a pronounced softening of low-frequency phonons at elevated pressures, which induces strong electron–phonon coupling and serves as the key driving force for superconductivity in this system. This work not only elucidates the superconducting mechanism in LaB₂H₈ but also highlights the importance of covalent hydrogen-based motifs in designing new high-T_c superconductors.