Recent developments of novel Fe-based superconductors

This paper presents recent progress in the study of novel Fe-based superconductors. We report a new Fe-based superconductor K0.8Fe1.7Se2, which was synthesized by intercalating the alkali-metal K into FeSe layers. Its superconducting transition temperature is 30K, which is the highest value at ambient pressure among the FeSe-based materials. Meanwhile, a superconducting phase with a transition temperature of 43K also emerges in this system, but the effort to make a pure sample composed of this 43K phase has not yet been successful. Furthermore, the effect of magnetic Co-doping on the superconductiing behavior is also reported. The results may have important implications for understanding the superconducting mechanism and exploring these new Fe-based superconductors.