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.Comment: 5 figure
