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 (11)

• 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
• Transition of stoichiometricSr2VO3FeAs to a superconducting state at 37.2 K
• Phase Separation and Magnetic Order in K-doped Iron Selenide Superconductor
• The effect of varying Fe-content on transport properties of K intercalated iron selenide KxFe2-ySe2
• 57-Fe Mossbauer study of magnetic ordering in superconducting K_0.85Fe_1.83Se_2.09 single crystals
• Anisotropic Hc2 of K0.8Fe1.76Se2 determined up to 60 T
• Anisotropic magnetism, resistivity, London penetration depth and magneto-optical imaging of superconducting K0.80Fe1.76Se2 single crystals

Cited by in corpus (18)

• Phase relations in K_xFe_{2-y}Se_2 and the structure of superconducting K_xFe_2Se_2 via high-resolution synchrotron diffraction
• Influence of microstructure on superconductivity in K${}_x$Fe${}_{2-y}$Se${}_2$ and evidence for a new parent phase K${}_2$Fe${}_7$Se${}_8$
• Fe-vacancy order and superconductivity in PbO-type tetragonal β-Fe1-xSe
• Evolution of precipitate morphology during heat treatment and its implications for the superconductivity in KxFe1.6+ySe2 single crystals
• Effective doping and suppression of Fermi surface reconstruction via Fe vacancy disorder in KxFe2-ySe2
• Dependence of superconductivity in CuxBi2Se3 on quenching conditions
• Overview on the physics and materials of the new superconductor KxFe2-ySe2
• Strong and nonmonotonic temperature dependence of Hall coefficient in superconducting K${}_x$Fe${}_{2-y}$Se${}_2$ single crystals
• Spin reorientation in TlFe1.6Se2 with complete vacancy ordering
• Superconductivity and magnetism in RbxFe2-ySe2: Impact of thermal treatment on mesoscopic phase separation
• Temperature dependence of iron local magnetic moment in phase-separated superconducting chalcogenide
• Archimedean solid-like superconducting framework in phase-separated K0.8Fe1.6+xSe2 (0<=x<=0.15)
• Robust superconductivity and transport properties in (Li1-xFex)OHFeSe single crystals
• Evolution of superconductivity in isovalent Te-substituted KxFe2-ySe2 crystals
• Elucidating the magnetic and superconducting phases in the alkali metal intercalated iron chalcogenides
• Superconductivity at the vacancy disorder boundary in K${}_x$Fe${}_{2-y}$Se${}_2$
• Annealing Effect on Microstructure and Superconductivity of KxFeySe2 Synthesized by an Easy One-step Method
• Multiband behavior and non-metallic low-temperature state of K${}_{0.50}$Na${}_{0.24}$Fe${}_{1.52}$Se${}_2$