Abstract
Single crystals of were successfully grown using a chemical transport reaction in an extremely narrow temperature range. Here, we report a comparative study of polycrystalline and single-crystal samples. The electrical resistivity measured on polycrystalline samples shows a broad hump and clear drop at 80 and 1.7 K, which correspond to the formation of the charge density wave (CDW) and superconducting (SC) transition, respectively. For the single crystals, shows a sharp change at K, and the superconductivity is absent, in contrast to the polycrystalline samples. With the current flowing along the and directions, the coincidence of the linear temperature dependence of above strongly implies that the electron-electron scattering mechanism dominates the transport properties in a quasi-one-dimensional chain. Furthermore, a metal-semiconductor-like transition is confirmed below in . The drop observed at 4.3 K in for the single crystal with more defects (small residual resistivity ratio, large , and weak drop) provides direct evidence of a disorder-related SC fluctuation in the CDW system. With temperature decreasing, the carrier density exhibits a similar and rapid decrease below for flowing current in both the and directions, whereas an obvious enhancement of carrier mobility appears as . An analysis of x-ray photoelectron spectroscopy spectra suggests that the mixed-valence states of Hf and Te could be related to the CDW formation in the multichain system of .
1 More- Received 23 August 2017
- Revised 17 October 2017
DOI:https://doi.org/10.1103/PhysRevB.96.174510
©2017 American Physical Society