Multiple-Intercalation Stages and Universal T_c Enhancement through Polar Organic Species in Electron-Doped 1T-SnSe₂

In this work, we report multiple-intercalation stages and universal Tc enhancement of superconductivity in 1T-SnSe2 through Li and organic molecule co-intercalation. We observe significantly increased lattice parameters of up to 40 Å and a dramatically enlarged interlayer distance of up to ∼11 Å in Li and N,N-dimethylformamide (DMF) co-intercalated SnSe2. Well-separated co-intercalation stages with different stacking patterns have been discovered by carefully controlled reaction times and concentrations of solutions. These co-intercalation stages are superconductors showing different superconducting signals. In addition, Li and various organic species such as acetone, dimethyl sulfoxide (DMSO), and tetrahydrofuran (THF) have been co-intercalated into SnSe2 crystals; all of which show an enhanced superconducting Tc compared to solely Li-intercalated SnSe2. Our findings may provide more insight into effectively tuning the electronic structure of the lamellar structure through organic molecule co-regulation and open a new strategy to engineer the physical properties of these layered materials by controlling their different intercalation stages.