Hallmark features of conventional BCS superconductivity in 2H-TaS2

Abstract

Abstract Layered transition metal dichalcogenides (TMDs) are model systems to investigate the interplay between superconductivity and the charge density wave (CDW) order. Here, we use muon spin rotation and relaxation ( μ + SR) to probe the superconducting ground state of polycrystalline 2H-TaS 2 , which hosts a CDW transition at 76 K and superconductivity below 1 K. The μ + SR measurements, conducted down to 0.27 K, are consistent with a nodeless, BCS-like single-gap s -wave state. Fits to the temperature dependence of the depolarization rate and Knight shift measurements support spin-singlet pairing. Crucially, no evidence of time-reversal symmetry breaking (TRSB) is observed, distinguishing 2H-TaS 2 from polymorphs like 4Hb-TaS 2 , where TRSB and unconventional superconductivity have been reported. These findings establish 2H-TaS 2 as a canonical BCS superconductor and provide a reference point for understanding the diverse electronic ground states that emerge in structurally distinct TMD polymorphs.