Large enhancement of the CDW resistivity anomaly and traces of superconductivity in imperfect samples of NbTe4

Abstract Transition metal chalcogenides usually crystallize in low-dimensional structures that frequently host electronic instabilities such as charge density waves (CDW) and superconductivity. Among them is NbTe 4 . This compound is a quasi-one-dimensional conductor that exhibits successive CDW transitions and superconductivity at 2.2 K when hydrostatic pressure is applied. The binary Nb-Te phase diagram predicts that this compound is non-stoichiometric and exists within a Te composition range. This work presents a systematic investigation of the physical properties of NbTe 4-δ polycrystalline samples. Electrical resistivity measurements show a large enhancement of the anomaly related to the CDW transition in the vicinity of 200 K. Further characterization demonstrates that Te deficiency can also induce superconductivity in this compound at 5.5 K and coexists with the CDW state.