Superconductivity in Li-intercalated 1T−SnSe2 driven by electric field gating

Creating carrier reservoirs in layered compounds can effectively tune the carrier density, which often induces a variety of emergent properties. Based on solid-ion-conductor gating technique, we successfully induce superconductivity of 4.8 K in ultrathin Li-intercalated ${\mathrm{SnSe}}_{2}$ samples. The ${\mathrm{Li}}^{+}$ ions are driven in between interspacing of ${\mathrm{SnSe}}_{2}$ layers and form a single reservoir layer to provide electrons. In addition, a domelike ${T}_{c}$ is found through substituting S for Se, where the optimal ${T}_{c}$ is 6.2 K for ${\mathrm{SnSe}}_{1.8}{\mathrm{S}}_{0.2}$. Density-functional theory calculations confirm that the intercalated ${\mathrm{LiSnSe}}_{2}$ is thermodynamically favorable, where the intercalation of Li expands the interlayer spacing by 10% and increases the carrier density by two orders of magnitude. Meanwhile, the calculated results reveal that the enhanced electron-phonon interaction due to softened phonons determines the occurrence of superconductivity. Our results demonstrate that this strategy is very effective to explore superconductors in layered materials with narrow band gaps.