Crystal growth, superconductivity, and charge density wave of pristine and Pd-intercalated 2H-TaS2

Here, pristine and Pd-intercalated 2H-TaS2 single crystals with (00l) orientation were grown by the chemical vapor transport technique. The superconductivity (SC) and charge density wave (CDW) were characterized by magnetic and electrical transport measurements. We find that SC and CDW in the pristine 2H-TaS2 condense respectively at transition temperatures Tc - 0.8 K and TCDW -78 K. The CDW order is completely suppressed, and Tc is greatly enhanced to 4.5 K in 2H-Pd0.04TaS2, which concludes a competing relation between the two collective electronic states. The positive Hall coefficient RH for both samples above 78 K indicates that hole-type carriers dominate the transport properties, and almost the same RH reveals tiny charge transfer between the intercalant Pd and the host TaS2. The difference of RH below 78 K between TaS2 and Pd0.04TaS2 is attributed to the reconstruction of the Fermi surface by Pd-intercalation-induced collapse of the CDW order. Therefore, the prominently improved Tc in 2H-Pd0.04TaS2 is mainly caused by the change of electronic structure due to the suppression of the CDW state rather than charge injection by Pd intercalation.