Electrical properties of NbTe4 and TaTe4

Pressure induced superconductivity bordering a charge-density-wave state in NbTe4 with strong spin-orbit coupling

“…2a. At T * = 200 K a cusp is observed, consistent with the previous reports [39,40]. It is known that the two incommensurate superlattices with − → q 1 = (0, 0,0.311c*) and − → q 2 = (0.5a*, 0.5b*, 0.344c*) are stable at room temperature in NbTe 4 .…”

“…In zero field, the room temperature resistivity is 59.2 µΩ·cm and decreases to 9.4 µΩ·cm at T = 2 K, yielding a residual resistivity ratio (RRR) of 6.3. Low RRR in NbTe 4 single crystals has been commonly reported, which is irrespective of growth conditions [39,40]. To understand the origin of the poor RRR, we performed the measurements of energy dispersive X-ray spectroscopy (EDXS).…”

Coexisting one-dimensional and three-dimensional spectral signatures inTaTe4

“…The resistivity exhibits a metalliclike behavior down to the lowest temperature measured. Data for the perpendicular directions ͑not shown͒ indicate that the resistivity is isotropic within the experimental uncertainty, in good agreement with previous data 20 . Figure 1 illustrates the optical conductivity at 15 and 300 K both perpendicular ͑upper panel͒ and parallel ͑lower panel͒ to the chain direction, with Drude-Lorentz fits for the low temperature data.…”

“…31 A multiband situation is also suggested by measurements of the thermal conductivity, which changes sign with temperature. 20 In this case only the tails of these overlapping bands could be observed by ARPES, smeared by the finite angular acceptance of Ϯ1°. This corresponds to Ϸ10% of the undistorted Brillouin zone, but 30% of the reduced zone for this material.…”

“…Simple chemistry considerations suggest that this band is half filled (d 1 configuration͒, but 1/3 filling has also been claimed to explain the observed CDW periodicity. 20 As we show below, the resistivity indicates a threedimensional metallic system. Similarly, optical conductivity data indicate a three-dimensional metal with almost free carriers.…”