Probing enhanced superconductivity in van der Waals polytypes of VxTaS2

Layered transition metal dichalcogenides (TMDs) stabilize in multiple structural forms with profoundly distinct and exotic electronic phases. Interfacing different layer types is a promising route to manipulate TMDs' properties, not only as a means to engineer quantum devices but also as a route to explore fundamental physics in complex matter. Here we use angle-resolved photoemission (ARPES) to investigate a strong layering-dependent enhancement of superconductivity in TaS2, in which the superconducting transition temperature, Tc, of its 2H structural phase is nearly tripled when insulating 1T layers are inserted into the system. The study is facilitated by a vanadium-intercalation approach to synthesizing various TaS2 polytypes, which improves the quality of the ARPES data while leaving key aspects of the electronic structure and properties intact. The spectra show the clear opening of the charge density wave gap in the pure 2H phase and its suppression when 1T layers are introduced to the system. Moreover, in the mixed-layer 4Hb system, we observe a strongly momentum-anisotropic increase in electron-phonon coupling near the Fermi level relative to the 2H phase. Both phenomena help to account for the increased Tc in mixed 2H/1T layer structures.