Emergent superconductivity in two-dimensional NiTe2 crystals

Two-dimensional superconductors exfoliated from layered materials harbor novel superconductivity and exotic correlated phases, often concomitantly, but their discovery has been few and far between. Employing the anisotropic Migdal-Eliashberg formalism based on ab initio calculations, we find monolayer NiTe2 to be an intrinsic superconductor with a T-c similar to 5.7 K, although the bulk crystal is not known to superconduct. Remarkably, bilayer NiTe2 intercalated with lithium is found to display two-gap superconductivity with a critical temperature T-c similar to 11.3 K and a superconducting gap of similar to 3.1 meV, arising from a synergy of electronic and phononic effects. As monolayer and bilayer NiTe2 have been recently isolated experimentally, and lithium can be inserted into the bilayer via ionic liquid gating, the comparatively high T-c, substrate independence, and proximity tunability will make these superconductors ideal platforms for exploring intriguing correlation effects and quantum criticality associated two-dimensional superconductivity.