Overview on the physics and materials of the new superconductor KxFe2-ySe2

Abstract

Since the discovery of high temperature superconductivity in iron pnictides in early 2008, many iron-based superconductors with different structures have been discovered, with the highest transition temperature to date being 57 K. By the end of 2010, another kind of new superconductor, the Fe-based chalcogenide K1-xFe2-ySe2 was discovered. A naive counting of the electrons in the system would lead to a conclusion that the system is heavily electron overdoped (~0.4 e/Fe). Band structure calculations further support this speculation and predict that the hole pockets which are found in the iron pnictides may be missing. This greatly challenges the widely perceived picture that the superconducting pairing is established by exchanging anti-ferromagnetic spin fluctuations and the electrons are scattered between the electron and hole pockets. Later, it was found that both potassium and iron might be deficient in K1-xFe2-ySe2, yielding to a picture of phase separation. In this picture the superconducting phase and the antiferromagnetic (AF) phase may phase separate spatially into different regions. This generates further curiosity about what is the real superconducting phase, what is the relationship between the superconducting phase and the AF phase, and what is the parent state for the superconducting phase. We propose a "spider web" model for the phase separation, which can explain both the transport and magnetic data. In this paper, we review the status of research in this rapidly growing field and list the important and unsettled issues as perspectives for future research.

arXiv comment23 pages, 6 figures, to appear in Report Progress in Physics

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Cited by in corpus (21)

• Recent advances in iron-based superconductors toward applications
• Iron-Based Superconductors: current status of materials and pairing mechanism
• Quantum critical point lying beneath the superconducting dome in iron-pnictides
• Superconducting Phases in Potassium-Intercalated Iron Selenides
• 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${}_8$
• Crystal Chemistry and Structural Design of Iron-Based Superconductors
• Spin fluctuations and superconductivity in KxFe{2-y}Se2
• Spectromicroscopy of electronic phase separation in K${}_x$Fe${}_{2-y}$Se${}_2$ superconductor
• Strong and nonmonotonic temperature dependence of Hall coefficient in superconducting K${}_x$Fe${}_{2-y}$Se${}_2$ single crystals
• Collective modes in multiband superconductors: Raman scattering in iron selenides
• Understanding doping, vacancy, lattice stability and superconductivity in KxFe2-ySe2
• Electronic structure of iron-based superconductors: from pnictides to chalcogenides and other similar systems
• Power Law Like Correlation between Condensation Energy and Superconducting Transition Temperatures in Iron Pnictide/Chalcogenide Superconductors: Beyond the BCS Understanding
• LDA'+DMFT Investigation of Electronic Structure of K{1-x}Fe{2-y}Se2 Superconductor
• Doping Dependence of Correlation Effects in K{1-x}Fe{2-y}Se2 Superconductor: LDA'+DMFT Investigation
• Magnetic anisotropic energy gap and low energy spin wave excitation in antiferromagnetic block phase of K2Fe4Se5
• The weak electronic correlations and absence of heavy Fermion state in KNi${}_2$Se${}_2$
• Phase-separation control of K${}_x$Fe${}_{2-y}$Se${}_2$ superconductor through rapid-quenching process
• Nonmetallic Low-Temperature Normal State of K0.70Fe1.46Se1.85Te0.15
• Annealing Effect on Microstructure and Superconductivity of KxFeySe2 Synthesized by an Easy One-step Method
• Magnon-induced superconductivity in field-cooled spin-1/2 antiferromagnets