Anisotropic multichain nature and filamentary superconductivity in the charge density wave system HfTe3

Abstract

Single crystals of HfTe3 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 ρ(T) 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, ρ(T) shows a sharp change at TCDW=93 K, and the superconductivity is absent, in contrast to the polycrystalline samples. With the current flowing along the a and b directions, the coincidence of the linear temperature dependence of ρ(T)/ρ(300K) above TCDW 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 TCDW in ρc. The drop observed at 4.3 K in ρb(T) for the single crystal with more defects (small residual resistivity ratio, large ρ0, 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 TCDW for flowing current in both the a and b directions, whereas an obvious enhancement of carrier mobility appears as I∥b. 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 HfTe3.

Source-reported materials — not catalogue approval

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