Organic-ion-intercalated FeSe-based superconductors

Abstract

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 ${(\mathrm{CTA})}_{0.3}\mathrm{FeSe}$ with ${T}_{c}$ as high as 45 K is synthesized by an electrochemical intercalation method. The as-prepared ${(\mathrm{CTA})}_{0.3}\mathrm{FeSe}$ 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 ${(\mathrm{CTA})}_{0.3}\mathrm{FeSe}$ is confirmed by magnetic susceptibility. Furthermore, a negative pressure effect on superconductivity $d{T}_{c}/dP=\ensuremath{-}5$ 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 ${T}_{c}$.