Competition of superconductivity and charge density wave order in NaxTaS2 single crystals

A series of crystals of NaxTaS2 with different superconducting transition temperatures (Tc) ranging from 2.0-4.4 K were obtained by flux method. The structural data deduced from X-ray diffraction pattern shows that the sample has the same structure as 2H-TaS2. Compared with the resistivity curve of un-intercalated sample 2H-TaS2 (Tc=0.8 K, TCDW≈70 K), no signal of charge density wave (CDW) was observed in our present samples Na0.1TaS2. It is thus concluded that there is a competition between the superconductivity and the CDW. With the increase of sodium content, the rise of Tc in NaxTaS2 is caused mainly by the suppression to the CDW in 2H-TaS2, and the conventional rigid band model for layered dichalcogenide may be inadequate to explain the changes induced by the slight intercalation of sodium in 2H-TaS2.