Relationship between charge density wave, filamentary superconductivity and bulk superconductivity in ZrTe3

Abstract

We investigated the relationship between a charge density wave (CDW) with a transition temperature (TCDW) of ∼ 60 K, filamentary superconductivities (SCs) along the a-axis and the b-axis with transition temperatures (TC's) of ∼ 3.5 K, and a bulk SC with a Tc below 2.5 K in ZrTe3, by measuring electrical resistance and magnetization for several crystals synthesized at different growth temperatures. As the growth temperature increased, the TCDW decreased, the TC of the bulk SC increased, and the TC's of the filamentary SCs did not show a clear change. The anisotropy of the upper critical field HC2 was different between the filamentary SCs and the bulk SC. These differences in the growth temperature dependence of TC and the anisotropy of HC2 indicate that the filamentary SCs are unrelated to the bulk SC. Moreover, the growth temperature dependence of the transition temperatures indicates that the CDW has a competitive relationship with the bulk SC, but a non-competitive coexistence with the filamentary SCs. Based on the anisotropies of HC2, we also infer that the filamentary SCs and the bulk SC occur on quasi-one-dimensional Fermi surfaces and a three-dimensional Fermi surface, respectively, and that the relationship between the three states in ZrTe3 cannot be explained solely in terms of conventional competition for a Fermi surface.