Superconductivity in palladium-doped 2H-TaS2

A series of PdxTaS2 (0.01 ≤ x ≤ 0.08) samples were prepared and characterized via scanning electron microscope, x-ray powder diffraction, resistivity, magnetization and specific heat measurements. The lattice parameter c associated with the interlayer distance increases monotonically with the Pd content while the parameter a remains essentially constant. The crystal structure of Pd0.08TaS2 has been determined and refined by Rietveld refinement. Pd0.08TaS2 is hexagonal (space group: P31c) with lattice parameters a = 3.3151(1) Å, c = 12.1497(9) Å. The superconducting transition temperature Tc (0.8 K) of TaS2 can be dramatically enhanced by Pd doping, and the maximum Tc of 4.2 K, about five times the Tc of pure TaS2, is obtained in Pd0.04TaS2. We have determined the superconducting parameters of Pd0.04TaS2, and found that the enhancement of Tc can be attributed to the increase of density of states at the Fermi level. The charge density wave (CDW) of TaS2 is gradually suppressed with Pd doping and disappears in Pd0.06TaS2. This suggests that there is a competitive interplay between superconductivity and CDW in this system.