Enhanced superconducting transition temperature in the water-intercalated sulfides

Water-intercalated misfit-layer sulfides Na-x(H2O)(y)(MS)(t+delta)(TaS2)(2) were found to exhibit superconductivity for M = Sn, Pb, and Sb, as well as anhydrate sulfides (MS)(1+delta)(TaS2)(2) with M = Pb, Sb, and Bi. The optimal transition temperature T, was similar or equal to 3 K for the anhydrate sulfides, and was enhanced up to similar or equal to 4 K by intercalating a bilayer of water between the adjacent TaS2 layers. This indicates that the presence of water molecule is favorable to superconductivity in the sulfides as in the cobalt oxide NaxCoO2 center dot nH(2)O, for which superconductivity appears only for the bilayer hydrate.