Superconductivity in Ta3Pd3Te14 with quasi-one-dimensional PdTe2 chains.

Superconductivity (SC) in low-dimensional systems attracts sustained attention in SC community. The discovery of first layered cuprate superconductor (La, Ba)2CuO41, has set off a wave of exploring high-Tc superconductors. Since after, a number of new superconductors with low dimensional structures, such as quasi-two-dimensional (Q2D) strontium ruthenate2, ferroarsenides3, bismuth oxysulfides4, quasi-one-dimensional (Q1D) transition-metal chalcogenides5, ternary tellurides6,7, and newly discovered chromium-based compounds8, were reported to display the features of novel SC. The spin (charge) fluctuations9,10, strong electron-electron correlations11, or metal-insulator boundaries12 among low-dimensional systems constitute the newly strategic prerequisites to explore high-Tc superconductors. Generally, the presence of some transition metal elements among them, which bear strong electron correlations, are believed to play a significant role in producing the exotic pairing glue. Owing to the inherent nature of transition metal chalcogenides13, the low-dimensional structures and rich physical properties, e.g., density-wave instability14, thermoelectricity15, and SC5, are prevalent among them. The tellurides, as compared with sulfides or selenides, are quite special in terms of its structures and properties because of the diffuse nature of the tellurium orbitals, and thus far rarely studied. Recently, we reported the observation of SC with Tc = 4.6 K in a ternary telluride Ta4Pd3Te16 with Q1D PdTe2 chains6. The detailed studies of its pairing symmetry were followed in applying the techniques of scanning tunneling microscopy16, low-temperature heat capacity17 and thermal conductivity18. The results indicate an anisotropic gap structure with the possible presence of nodes, although electronic structure calculations show the contributions of Pd 4d electrons to the density of states at Fermi level are pretty small19. From a crystal-structure viewpoint, Ta4Pd3Te16 also belongs to a layered compound resulting from the condensation of Pd-based octahedral chains, Ta-based bicapped trigonal prismatic chains, and Ta-based double octahedral chains6,20. If the Ta-based double octahedral chains are replaced by Ta-based single octahedral chains, the condensation of the three different types of chains would form the atomic layer of a new compound Ta3Pd3Te14, which was firstly synthesized by Liimatta and Ibers in 198921. The major difference between them in structure is well reflected from Fig. 1(f), which shows the projection view of one atomic layer of Ta3Pd3Te14 and Ta4Pd3Te16 along the b axis. The structural details of Ta3Pd3Te14 are discussed below. Then, considering the close structural relationship of this material with the superconductor Ta4Pd3Te16, a natural question is whether the former is as well a superconductor. Figure 1 Sample characterization and crystallographic structure of Ta3Pd3Te14. In this paper, we report the observation of SC with Tc = 1.0 K in layered ternary telluride Ta3Pd3Te14 with Q1D PdTe2 chains. The bulk SC was identified by the electronic heat capacity data, which shows an obvious anomaly at the transition temperature. The specific-heat jump ΔC/(γnTc) ≈ 1.35 indicates Ta3Pd3Te14 may be a weakly coupled superconductor. In addition, the result of low-temperature thermal conductivity measurements of Ta3Pd3Te14 crystal down to 80 mK suggests a dirty s-wave superconducting gap. We summarize our results by discussing the similarities and differences between the closely related superconductors of Ta3Pd3Te14 and Ta4Pd3Te16, and compiled an extended list of their physical properties.