Fe-vacancy order and superconductivity in PbO-type tetragonal β-Fe1-xSe

Abstract

Several superconducting transition temperatures in the range of 30-40 K were reported in the recently discovered intercalated FeSe sytem (A1-xFe2-ySe2, A = K, Rb, Cs, Tl). Although the superconducting phases were not yet conclusively decided, more than one magnetic phase with particular orders of iron vacancy and/or potassium vacancy were identified, and some were argued to be the parent phase. Here we show the discovery of the presence and ordering of iron vacancy in nonintercalated FeSe (PbO-type tetragonal β-Fe1-xSe). Three types of iron-vacancy order were found through analytical electron microscopy, and one was identified to be nonsuperconducting and magnetic at low temperature. This discovery suggests that the rich-phases found in A1-xFe2-ySe2 are not exclusive in Fe-Se related superconductors. In addition, the magnetic β-Fe1-xSe phases with particular iron-vacancy orders are more likely to be the parent phase of FeSe superconducting system, instead of the previously assigned β-Fe1+δTe.

23 pages, 6 figures. PNAS Early Edition (2013)

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• A Mott insulator continuously connected to iron pnictide superconductors
• Extreme anisotropy and anomalous transport properties of heavily electron doped Lix(NH3)yFe2Se2 single crystals
• Enhancement of Transition Temperature in FexSe0.5Te0.5 Film via Iron Vacancies
• Structure and composition of the superconducting phase in alkali iron selenide K${}_y$Fe${}_{1.6+x}$Se${}_2$
• Thermoelectric properties of iron-based superconductors and parent compounds
• Tuning stoichiometry and its impact on superconductivity of monolayer and multilayer FeSe on SrTiO3
• Temperature-induced band selective localization and coherent-incoherent crossover in single-layer FeSe/Nb:BaTiO3 /KTaO3
• Emergence of magnetism and controlling factors of superconductivity in Li/Na-ammonia co-intercalated FeSe1-zTez
• Disordered Fe vacancies and superconductivity in potassium-intercalated iron selenide (K2-xFe4+ySe5)
• Tunable Fe-vacancy disorder-order transition in FeSe thin films
• Effect of nominal substitution of transition metals for excess Fe in Fe_{1+x}Se superconductor
• Stoichiometry and defect superstructures in epitaxial FeSe films on SrTiO3
• Insulator-like behavior coexisting with metallic electronic structure in strained FeSe thin films grown by molecular beam epitaxy
• Microstructural control of the transport properties of $\beta$-FeSe films grown by sputtering
• Role of the Extra-Fe in K2-xFe4+ySe5 superconductors
• Pair-checkerboard antiferromagnetic order in $\beta$-Fe${}_4$Se${}_5$ with $\sqrt{5}\times \sqrt{5}$ ordered Fe vacancies
• Quasi-uniaxial pressure induced superconductivity in stoichiometric compound UTe${}_2$
• Analysis of nonlinear conductivity of point contacts on the base of FeSe in the normal and superconducting state
• In-situ topotactic chemical reaction for spectroscopies
• Connection between ambient-pressure and pressure-induced superconducting phases in alkaline iron selenide superconductors
• Fe-vacancy ordered Fe4Se5: The insulating parent phase of FeSe superconductor
• Magnetotransport studies of FeSe under hydrostatic pressure