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∼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∼11.3 K and a superconducting gap of ∼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.