Superconductivity at 41.0 K in the F-doped LaFeAsO1-xFx
  Here we report the superconductivity in the LaFeAsO1-xFx system prepared by high pressure synthesis. The highest onset superconducting transition temperature (Tc) in this La-based system is 41.0 K with the nominal composition of LaFeAsO1-xFx (x = 0.6), which is higher than that reported previously by ambient pressure synthesis. The increase of Tc can be attributed to the further shrinkage of crystal lattice that causes the stronger chemical pressure on the Fe-As plane, which is induced by the increased F-doping level under high pressure synthesis. 
Wei Lu, Xiao-Li Shen, Jie Yang, Zheng-Cai Li, Wei Yi, Zhi-An Ren,   Xiao-Li Dong, Guang-Can Che, Li-Ling Sun, Fang Zhou, Zho...