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 wereobtained 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 signalof 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 Nax TaS2 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.