"Cigar" Fermi surface as a possible requisite for superconductivity in iron-based superconductors

Abstract

Recently discovered A-Fe-Se (A - alkali metal) materials have questioned the most popular theories of iron-based superconductors because of their unusual electronic structure [1]. Controversial photoemission data taken in the superconducting state [2-7] are in conflict with highly magnetic state seen by neutron-, muSR-spectroscopies and transport/thermodynamic probes [8-10]. These results lead to suggestions to consider all iron-based materials as originating from Mott-insulators or semiconductors, thus once again raising the question of close relation between the cuprates and Fe-based superconductors [e.g. 2]. Here we study electronic and magnetic properties of Rb0.77Fe1.61Se2 (Tc = 32.6 K) in normal and superconducting states by means of photoemission and muSR spectroscopies as well as band structure calculations. We demonstrate that the puzzling behavior of these novel materials is the result of separation into metallic (~12%) and insulating (~ 88%) phases. Only the former becomes superconducting and has a usual electronic structure of electron-doped FeSe-slabs. Our results thus imply that the antiferromagnetic insulating phase is just a byproduct of Rb-intercalation and its magnetic properties have hardly any relation to the superconductivity. Instead, we find that also in this, already third class of iron-based compounds, the key ingredient for superconductivity is a certain proximity of a van Hove singularity to the Fermi level. These findings set the direction for effective search of new superconducting materials.

11 pages, PDF format, Related work: http://www.ifw-dresden.de/institutes/iff/research/SC/arpes

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Cited by in corpus (12)

• Unusual band renormalization in the simplest iron based superconductor
• Pseudogap from ARPES experiment: three gaps in cuprates and topological superconductivity
• Interaction-induced singular Fermi surface in a high-temperature oxypnictide superconductor
• Metamorphoses of electronic structure of FeSe-based superconductors (Review article)
• Optical conductivity of iron-based superconductors
• Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs
• Electronic band structure of optimal superconductors: from cuprates to ferropnictides and back again
• Observation of a Hidden Hole-Like Band Approaching the Fermi Level in K-Doped Iron Selenide Superconductor
• Importance of dxy orbital and electron correlation in iron-based superconductors revealed by phase diagram for 1111-system
• Tuning orbital-selective correlation effects in superconducting Rb${}_{0.75}$Fe${}_{1.6}$Se${}_{2-z}$S${}_z$
• Direct observation of spin-orbit coupling in iron-based superconductors
• Phase separation in iron chalcogenide superconductor Rb0.8+xFe1.6+ySe2 as seen by Raman light scattering and band structure calculations