Three Dimensional Superconductivity in FeSe with Tczero Up to 10.9 K Induced by Internal Strain

Polycrystalline sample FeSe was synthesized by a self-flux solution method which shows a zero resistance temperature up to 10.9 K and a Tconset (90% rhon, rhon: normal state resistivity) up to 13.3 K. The decrease of superconducting transition temperature by heat treatment indicates that internal crystallographic strain which plays the same effect as external pressure is the origin of its high Tc. The fluctuation conductivity was studied which could be well described by 3D Aslamazov-Larkin (AL) power law. The estimated value of coherence length xic=9.2 AA is larger than the distance between conducting layers (~6.0 AA), indicating the three-dimensional nature of superconductivity in this compound.

Superconductivity in nickel-based compound GdONiBi and hole doped Gd0.9Sr0.1ONiBi

We successfully synthesized the nickel-based compound GdONiBi with superconducting transition temperature about 4.5 K. By partially substituting the element Gd with Sr to introduce holes into the material, we got new superconductor Gd0.9Sr0.1ONiBi with critical temperature about 4.7 K. The normal state resistivity in nickel-based samples shows a metallic behavior. The magnetoresistance measurements show a different behavior compared to those in iron-based compounds which indicates that the mechanism in the two kinds of superconductors maybe different.