Metastable superconducting state in quenched KxFe2-ySe2

Abstract

By direct quenching or post-annealing followed by quenching, we have successfully obtained a series of KxFe2-ySe2 samples with different properties. It is found that the samples directly quenched in the cooling process of growth show superconductivity and the one cooled with furnace is insulating even though their stoichiometries are similar. The sample cooled with furnace can be tuned from insulating to superconducting by post-annealing and then quenching. Based on the two points mentioned above, we conclude that the superconducting state in KxFe2-ySe2 is metastable, and quenching is the key point to achieve the superconducting state. The similar stoichiometries of all the non-superconducting and superconducting samples indicate that the iron valence doesn't play a decisive role in determining whether a KxFe2-ySe2 sample is superconducting. Combining with the result got in the KxFe2-ySe2 thin films prepared by molecular beam epitaxy (MBE), we argue that our superconducting sample partly corresponds to the phase without iron vacancies as evidenced by scanning tunnelling microscopy (STM) and the insulating sample mainly corresponds to the phase with the $\sqrt{5}\times \sqrt{5}$ vacancy order. Quenching may play a role of freezing the phase without iron vacancies.

9 pages, 7figures, this article is a new version of arXiv:1103.1347 with new data added

References in corpus (5)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• The superconductivity at 18 K in LiFeAs system
• Superconductivity up to 37 K in (A1-xSrx)Fe2As2 with A=K and Cs
• LiFeAs: An Intrinsic FeAs-based Superconductor with Tc = 18K
• Fe-based high temperature superconductivity with Tc=31K bordering an insulating antiferromagnet in (Tl,K)FexSe2 Crystals

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• Dependence of superconductivity in CuxBi2Se3 on quenching conditions
• Overview on the physics and materials of the new superconductor KxFe2-ySe2
• Spin reorientation in TlFe1.6Se2 with complete vacancy ordering
• Superconductivity and magnetism in RbxFe2-ySe2: Impact of thermal treatment on mesoscopic phase separation