Superconductivity induced by hydrogen anion substitution in 1111-type iron arsenides

Abstract

Hydrogen is the simplest bipolar element and its valence state can be controlled from +1 to -1. We synthesized the 1111-type CaFeAsH and LnFeAsO1-xHx (Ln = lanthanide) with the ZrCuSiAs type structure by a high-pressure synthesis method. The position and valence state of the substituted H were determined by neutron diffraction and density functional theory calculations. The close similarity in the structural and electrical properties of CaFeAsH and CaFeAsF indicated the formation of the hydride ion (H-), which is isovalent with the fluoride ion (F-), in the 1111-type iron arsenides. When some of the O2- ions in LnFeAsO are replaced by H-, superconductivity is induced by electron doping to the FeAs-layer to maintain charge neutrality. Since the substitution limit of hydrogen in LnFeAsO (x~0.5) is much higher than that of fluorine (x~0.2), the hydrogen substitution technique provides an effective pathway for high-density electron-doping, making it possible to draw the complete electronic phase diagram of LnFeAsO. The x-T diagrams of LnFeAsO1-xHx (Ln = La, Ce, Sm, Gd) have a wide superconducting (SC) region spanning the range x = 0.04 to 0.4, which is far from the parent antiferromagnetic region near x = 0.0. For Ln=La, another SC dome region was found in the range x = ~ 0.2 to ~0.5 with a maximum Tc = 36 K, in addition to a conventional SC dome located at x ~0.08 with maximum Tc = 29 K. Density functional theory calculations performed for LaFeAsO1-xHx indicated that the newly observed Tc is correlated with the appearance of degeneration of the Fe 3d bands (dxy, dyz and dzx), which is caused not only by regularization of the tetrahedral shape of FeAs4 due to chemical pressure effects but also by selective band occupation with doped electrons. In this article, we review the recent progress of superconductivity in iron (oxy)arsenides and related compounds induced by hydrogen substitution.

to appear in Current Opinion. Solid State and Materials Science

References in corpus (30)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Magnetic Order versus superconductivity in the Iron-based layered La(O1-xFx)FeAs systems
• Superconductivity at 43 K in Samarium-arsenide Oxides $SmFeAs{O}_{1-x}{F}_x$
• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Superconductivity at 41 K and its competition with spin-density-wave instability in layered CeO${}_{1-x}$F${}_x$FeAs
• Superconductivity and Phase Diagram in the Iron-based Arsenic-oxides ReFeAsO1-delta (Re = rare earth metal) without F-Doping
• Superconductivity in iron-based F-doped layered quaternary compound Nd[O1-xFx]FeAs
• Superconductivity at 52 K in iron-based F-doped layered quaternary compound Pr[O1-xFx]FeAs
• Superconductivity in Co-doped LaFeAsO
• Superconductivity at 17 K in (Fe2P2)(Sr4Sc2O6): a new superconducting layered pnictide oxide with a thick perovskite oxide layer
• Two-dome structure in electron-doped iron arsenide superconductors
• Effect of Co doping on superconductivity and transport properties in SmFe${}_{1-x}$Co${}_x$AsO
• Superconductivity induced by cobalt doping in iron-based oxyarsenides
• Different resistivity response to spin density wave and superconductivity at 20 K in $C{a}_{1-x}N{a}_{x}F{e}_{2}A{s}_2$
• Hydrogen in layered iron arsenide: indirect electron doping to induce superconductivity
• Nickel-based layered superconductor, LaNiOAs
• Strong-coupling superconductivity in layered nickel-based LaO${}_{1-x}$F${}_x$NiAs
• Superconductivity above 50K in LnFeAsO1-y (Ln= Nd, Sm, Gd, Tb and Dy) Synthesized by High-pressure Technique
• Synthesis, crystal structure and spin-density-wave anomaly of the iron arsenide-fluoride SrFeAsF
• SrFeAsF as a parent compound for iron pnictide superconductors
• Narrow superconducting window in Ni-doped LaFeAsO
• Cobalt-substitution-induced Superconductivity in a New Compound with ZrCuSiAs-type Structure, SrFeAsF
• Superconductivity in Fluorine-Arsenide Sr_{1-x}La_xFeAsF
• Magnetic order in CaFe1-xCoxAsF (x = 0, 0.06, 0.12) superconductor compounds
• Effect of 3d Transition Metal Doping on the Superconductivity in Quaternary Fluoroarsenide CaFeAsF
• Nd induced Mn spin-reorientation transition in NdMnAsO
• Comparison of crystal structures and effects of Co substitution in a new member of Fe-1111 superconductor family AeFeAsF(Ae = Ca and Sr): a possible candidate for higher Tc superconductor
• Colossal Magnetoresistance in the Mn2+ Oxypnictides NdMnAsO1-xFx
• Strong carrier-scattering in iron-pnictide superconductors with highest Tc obtained from charge transport experiments
• WDX-Analysis of the New Superconductors RO(1-x)F(x)FeAs and Its Consequences on the Electronic Phase Diagram

Cited by in corpus (9)

• Recent advances in iron-based superconductors toward applications
• Iron-Based Superconductors: current status of materials and pairing mechanism
• Controlling Factors of Tc-Dome Structure in 1111-Type Iron Arsenide Superconductors
• La-substituted CaFeAsH superconductor with Tc = 47 K
• Superconductivity in Uncollapsed Tetragonal LaFe2As2
• Three superconducting phases with different categories of pairing in hole- and electron-doped LaFeAs${}_{1-x}$P${}_x$O
• Multiple-pseudogap phases in hydrogen-doped LaFeAsO system
• High-pressure growth effects on the superconducting properties of Sm-based oxypnictide superconductors
• Neutron powder diffraction study on the non-superconducting phases of ThFeAsN${}_{1-x}$O${}_x$ ($x=0.15,0.6$) iron pnictide