A perspective on pnictide superconductors

Abstract

FeSe is employed as reference material to elucidate the observed high Tc superconducting behaviour of the related layered iron pnictides. The structural and ensuing semimetallic band structural forms are here rather unusual, with the resulting ground state details extremely sensitive to the precise shape of the Fe-X coordination unit. The superconductivity is presented as coming from a combination of Resonant Valence Bond (RVB) and Excitonic Insulator physics, and incorporating Boson-Fermion degeneracy. Although sourced in a very different fashion the latter leads to some similarites with the high temperature superconducting (HTSC) cuprates. The Excitonic Insulator behaviour sees SDW, CDW/PLD and superconductive instabilities all vie for ground state status. The conflict leads to a very sensitive and complex set of properties, frequently mirroring HTSC cuprate behaviour. The delicate balance between ground states is made particularly difficult to unravel by the micro-inhomogeneity of structural form which it can engender. It is pointed out that several other notable superconductors, layered in form, semimetallic with indirect overlap and possessing homopolar bonding, would look to fall into the same general category, beta-ZrNCl and MgB2 and the high-pressure forms of several elements, like sulphur, phosphorus, lithium and calcium, being cases in point.

53 pages, 11 figures

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Cited by in corpus (27)

• London Penetration Depth in Iron - based Superconductors
• Superconductivity in the iron selenide KxFe2Se2 (0 <= x <= 1)
• New ternary ThCr2Si2-type iron-selenide superconducting materials: synthesis, properties and simulations
• The intercalation chemistry of layered iron chalcogenide superconductors
• Electronic structure and Fermi surface of new K intercalated iron selenide superconductor KxFe2Se2
• Thin Film Growth and Device Fabrication of Iron-Based Superconductors
• Crystal Chemistry and Structural Design of Iron-Based Superconductors
• Microstructural magnetic phases in superconducting FeTe0.65Se0.35
• Crystal Structure of BaFe2Se3 as a Function of Temperature and Pressure: Phase Transition Phenomena and High-Order Expansion of Landau Potential
• Twisting of 2D kagomé sheets in layered intermetallics
• Search for pressure induced superconductivity in CeFeAsO and CeFePO iron pnictides
• Dynamics of Order Parameters near Stationary States in Superconductors with a Charge-Density Wave
• Stability, structural, elastic and electronic properties of polymorphs of the superconducting disilicide YIr2Si2
• Pressure-dependent magnetization and magnetoresistivity studies on the tetragonal FeS (mackinawite): revealing its intrinsic metallic character
• Quasiclassical description of a superconductor with a spin density wave
• Microstructural and transport properties of superconducting FeTe0.65Se0.35 crystals
• Local Structure of the Superconductor K0.8Fe1.6+xSe2: Evidence of Large Structural Disorder
• Incommensurate spin-density wave and multiband superconductivity in Na${}_x$FeAs as revealed by nuclear magnetic resonance
• Josephson-like spin current in junctions composed of antiferromagnets and ferromagnets
• Realization of the $\pi$-state in junctions formed by multi-band superconductors with a spin-density-wave
• High pressure transport studies of the LiFeAs analogues CuFeTe2 and Fe2As
• Elastic properties and inter-atomic bonding in new superconductor KFe2Se2 from first principles calculations
• The Superconducting Transition Temperatures of Fe1+xSe1--y, Fe1+xSe1--yTey and (K/Rb/Cs)zFe2--xSe2
• Charge compensation and optimal stoichiometry in superconducting (Ca${}_x$La${}_{1-x}$)(Ba${}_{1.75-x}$La${}_{0.25+x}$)Cu${}_3$O${}_y$
• Time-dependent equation for the magnetic order parameter near the quantum critical point in multiband superconductors with a spin density wave
• Tunable superconductivity in Fe-pnictide heterointerfaces by diffusion control
• Electronic properties of new low-temperature superconductors: 3.3K (Ni2P2)(Sr4Sc2O6) and 2.7K (Ni2As2)(Sr4Sc2O6) from first principles