Electrical properties of a quasi-one-dimensional compound Nb3Te4 inserted with indium: InxNb3Te4 Original Research Article

Resistivity, ρ and thermoelectric power, S of Nb3Te4 inserted with indium are studied. With addition of In, ρ remains largely unchanged, but S is greatly affected, indicating that the conduction band of Nb3Te4 consists of bands of electron- and hole-like carriers. Both ρ and S show anomalies at TR>100 K, around 84 K, and near 49 K, TR depending upon x. The characteristic of these anomalies is as follows: (i) The anomaly at TR>100 K appears at x<0.06 and x>0.08. The TR at x<0.06 is 113–121 K, being insensitive to x and agrees well with CDW formation temperature, TCDW of pure Nb3Te4. At x>0.08, a giant increase in ρ appears and TR changes continuously from TCDW of pure Nb3Te4 to that of highly inserted Nb3Te4. (ii) The anomaly at 84 K appears at x=0 and x≧0.2 and shows the second for x=0 and the first order phase transition for x≧0.2,TR being insensitive to x. The phase transition at x≧0.2 has been tentatively identified with the ordering of inserted In atoms. (iii) The anomaly at 49 K appears at x<0.13 and TR is insensitive to x. On the basis of multiband model the anomalous transport property of InxNb3Te4 is discussed in terms of charge–density-wave formation. The x dependence of TR can be explained in terms of the mean field approximation, in which softening of the lattice of InxNb3Te4 plays an important role as well as modification of the density of states at the Fermi level.