Intrinsic and doping-enhanced superconductivity in monolayer 1H-TaS2: Critical role of charge ordering and spin-orbit coupling

The interplay of superconductivity with charge density wave (CDW) in metallic transition-metal dichalcogenides has been widely debated, and viable strategies manipulating these quantum states in the two-dimensional (2D) limit remain unclear. Using the ab initio anisotropic Migdal-Eliashberg theory, we successfully explain the superconductivity observed in monolayer 1H-TaS2 by simultaneously determining its precise CDW structure and treating the marked modification of electron-phonon interaction and critical temperature Tc by spin-orbit coupling effects. With this paradigm, we further show that electron doping weakens the CDW order leading to increased Tc up to 11 K, along with a single-gap to two-gap superconductivity transition due to the suppression of the CDW gap. By contrast, a low hole doping barely affects the CDW but still yields a significantly enhanced superconducting order, implying their good coexistence. Combined with the synergistic behavior of CDW and superconductivity, which cooperate upon TaS2 thickness reduction causing an unusual rise of Tc, our results unravel diversified interactions between the two collective orders in ultrathin TaS2, being competition, coexistence or cooperation depending on external stimuli, which provide key clues for controlling correlated states in devices based on 2D CDW superconductors.