Pressure-induced superconductivity in Li-Te electrides

Electrides, which accommodate excess of electrons in lattice interstitials as anions, usually exhibit interesting properties and broad applications. Until now, most electrides, especially at high pressures, show semiconducting/insulating character arising from the strong localization of interstitial and orbital electrons. However, modulating their connectivity could turn them into metals and even superconductors. In this work, with the aid of first-principles particle swarm optimization, we have identified a series of pressure-induced Li-rich electrides in the Li-Te system, in which hollow ${\mathrm{Li}}_{n}$ polyhedra accommodate the excess of electrons. With increasing Li content, these electrides undergo an interesting structural evolution. Meanwhile, the connection type of ${\mathrm{Li}}_{n}$ polyhedra experiences transitions from vertex- or edge sharing, to face sharing, leading to a diverse distribution and connectivity of interstitial electrons. All identified electrides exhibit anionic electrons-dominated metallicity. More interestingly, ${\mathrm{Li}}_{9}\mathrm{Te}$, with the highest content of ${\mathrm{Li}}_{6}$ octahedra, is superconducting with a critical temperature $({T}_{\mathrm{c}})$ of 10.2 K at 75 GPa, which is much higher than typical electrides (e.g., $12\mathrm{CaO}\ifmmode\cdot\else\textperiodcentered\fi{}7{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$, ${\mathrm{Ca}}_{2}\mathrm{N}$, and ${\mathrm{Y}}_{2}\mathrm{C}$). Its superconductivity mainly originates from the coupling between hybridized electrons (anionic and atomic non-$s$-state ones) and Te-dominated phonons.