Synthesis of a new alkali metal-organic solvent intercalated iron selenide superconductor with Tc{\approx}45K

TL;DR

This paper reports the synthesis of a new iron selenide superconductor intercalated with alkali metals and organic molecules, achieving a Tc of approximately 45K, and explores how post-annealing enhances its superconducting properties.

Contribution

It introduces a novel intercalation method using organic compounds to significantly increase the critical temperature of iron selenide superconductors.

Findings

Superconductor with Tc ~45K synthesized via organic intercalation.

Post-annealing enlarges the c-parameter and enhances shielding fraction.

Intercalation with organic compounds can lead to higher Tc in FeSe-based materials.

Abstract

We report on a new iron selenide superconductor with a TC onset of 45K and the nominal composition Lix(C5H5N)yFe2-zSe2, synthesized via intercalation of dissolved alkaline metal in anhydrous pyridine at room temperature. This superconductor exhibits a broad transition, reaching zero resistance at 10K. Magnetization measurements reveal a superconducting shielding fraction of approximately 30%. Analogous phases intercalated with Na, K and Rb were also synthesized and characterized. The superconducting transition temperature of Lix(C5H5N)yFe2-zSe2 is clearly enhanced in comparison to the known superconductors FeSe0.98 (Tc ~ 8K) and AxFe2-ySe2 (TC ~ 27-32K) and is in close agreement with critical temperatures recently reported for Lix(NH3)yFe2-zSe2. Post-annealing of intercalated material (Lix(C5H5N)yFe2-zSe2) at elevated temperatures drastically enlarges the c-parameter of the unit cell (~44%) and increases the amount of superconducting shielding fraction to nearly 100%. Our findings indicate a new synthesis road leading to possibly even higher critical temperatures in this class of materials by intercalation of organic compounds between Fe-Se layers.