A novel iron-based superconductor synthesized by the ion exchange technique

Abstract

The superconductivity of the FeSe-based superconductor is extremely sensitive to Fe vacancies in the FeSe plane. In order to reduce the formation of Fe vacancies in the FeSe plane, various low-temperature methods are developed. However, it is still complex and time consuming to control the Fe vacancies concentration. Here, a hybrid iron-based superconductor, Li _0.21 Se _0.05 (EG) _0.26 FeSe (EG: ethylene glycol, C _2 H _6 O _2 ), is synthesized by a solvothermal ion-exchange technique using a nearly vacancy-free precursor of (TBA) _0.3 FeSe as the matrix. Bulk superconductivity with transition temperature ( T _c ) of 30 K is confirmed by the characterization with the magnetic susceptibility and resistivity measurements. Compared with the pristine FeSe single crystal, x-ray photoelectron spectroscopy results show a decrease of the Fe valence, indicating that electron doping to FeSe plane accounts for the increase of the T _c . Our result suggests that (TBA) _0.3 FeSe, a nearly vacancy-free precursor with a large distance between the adjacent FeSe planes, is a good template candidate for the synthesis of other hybrid iron-based superconductors using the ion exchange technique.

Keywords

• superconductivity
• FeSe-based superconductor
• ion exchange
• nearly vacancy-free precursor