Organic-ion-intercalated FeSe-based superconductors

Finding a new derivative structure of FeSe-based superconductors with a high superconducting transition temperature (T-c) is of great significance. Here, in this work, an organic-ion-[cetyltrimethyl ammonium (CTA(+))]-intercalated FeSe-based superconductor (CTA)(0.3)FeSe with T-c as high as 45 K is synthesized by an electrochemical intercalation method. The as-prepared (CTA)(0.3)FeSe has a hybrid crystal structure consisting of double layers of CTA(+) and one layer of FeSe, which is consistent with a lateral-bilayer model. The superconductivity of (CTA)(0.3)FeSe is confirmed by magnetic susceptibility. Furthermore, a negative pressure effect on superconductivity dT(c)/dP = -5 K/GPa is observed. This is the first pure organic-ion-intercalated FeSe-based superconductor with a high T-c and high crystallinity. Our work offers a new method to modify the interface interaction between the FeSe layer and the intercalator, and sheds new light on finding new FeSe-based superconductors with higher T-c.