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 (${\mathrm{CTA}}^{+}$)]-intercalated FeSe-based superconductor ${\left(\mathrm{CTA}\right)}_{0.3}\mathrm{FeSe}$ with $T_c$ as high as 45 K is synthesized by an electrochemical intercalation method. The as-prepared ${\left(\mathrm{CTA}\right)}_{0.3}\mathrm{FeSe}$ has a hybrid crystal structure consisting of double layers of ${\mathrm{CTA}}^{+}$ and one layer of FeSe, which is consistent with a lateral-bilayer model. The superconductivity of ${\left(\mathrm{CTA}\right)}_{0.3}\mathrm{FeSe}$ is confirmed by magnetic susceptibility. Furthermore, a negative pressure effect on superconductivity $d{T}_c/dP=-5$ 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 $T_c$.

• Received 26 February 2018
• Revised 11 May 2018

DOI:https://doi.org/10.1103/PhysRevMaterials.2.074801