Superconductivity, structure and resistivity in HgBa₂Ca₂Cu₃O_8+δ

Samples of HgBa₂Ca₂Cu₃O_8+δ were successfully prepared and investigated. By examining the X-ray diffraction, transmission electron microscopy, magnetization and resistivity, we found that HgBa₂Ca₂Cu₃O_8+δ possesses an orthorhombic structure with lattice parameters a=5.451 (2)Å, b=5.432 (2)Å and c=15.826 (7) Å and a sharp superconducting transition (magnetically determined) at ∼112 K as-synthesized and as high as ∼135 K after oxygenation. The resistivity vanishes below 134 K, the highest reported for any superconductor to date. No superstructures of the types previously reported in the > 130 K samples were detected in this study. A linear T-dependent resistivity which is interpolated to zero at 0 K was also observed above ∼240 K. Below ∼240 K, deviation from such a linearity appears, which may be attributable to the fluctuation or spin-scattering effect, assuming that the behavior is intrinsic to HgBa₂Ca₂Cu₃O_8+δ.