Superconductivity in Ca3H2 electride at moderate pressure

Abstract

The discovery of superconductivity electrides in hydrides has fueled enthusiasm due to their inherent physical characteristics generated from localized anionic electrons. In this work, using density functional theory (DFT), we discover a remarkable hydrogen-based electride superconductor Ca₃H₂ with the P63/mmc symmetry. The thermal stability and lattice dynamical stability of this novel electride have been confirmed by ab initio molecular dynamics simulations and phonon calculations. Interestingly, the superconducting critical temperature T_c of Ca₃H₂ increases with pressure and exhibits the highest T_c value of 8.4 K under 19.5 GPa, which shows distinguished superconductivity at a moderate pressure range compared with other electrides. Moreover, the mainly physical origin of the rise of T_c has been revealed, in which the electron occupancy of Ca-d orbitals increases their coupling with low-frequency phonons dominated by out-of-plane vibration with the increase of pressure. This work will enrich the realization of hydrogen-based electrides and shed light on the discovery of superconducting electrides at moderate pressures.