Unconventional superconductivity originating from disconnected Fermi surfaces in the iron-based compound

Abstract

The iron-based LaFeAsO${}_{1-x}$F${}_x$ recently discovered by Hosono's group is a fresh theoretical challenge as a new class of high-temperature superconductors. Here we describe the electronic structure of the material and the mechanism of superconductivity. We start with constructing a tight-binding model in terms of the maximally localized Wannier orbitals from a first-principles electronic structure calculation, which has turned out to involve all the five Fe 3d bands. This is used to calculate the spin and charge susceptibilities with the random phase approximation. The spin susceptibility has peaks around ${\Vec k} = (π, 0), (0, π)$ arising from a nesting across disconnected Fermi surface pockets. We have then plugged the susceptibilities into the linearised Eliashberg equation. For the doping concentration $x=0.1$, we obtain an unconventional s-wave pairing, which is roughly an extended s in that the gap changes sign between the Fermi pockets, but the gap function is actually a 5$\times$5 matrix. Its experimental implications are also discussed.

6 pages, 8 figures, Proc. Int. Conf. on Muon Spin Rotation, Relaxation and Resonance, Tsukuba, Japan, 2008

References in corpus (41)

• 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
• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• LaFeAsO${}_{1-x}$F${}_x$: A low carrier density superconductor near itinerant magnetism
• Observation of Fermi-surface-dependent nodeless superconducting gaps in Ba0.6K0.4Fe2As2
• Competing Orders and Spin-Density-Wave Instability in La(O${}_{1-x}$F${}_x$)FeAs
• Superconductivity in iron-based F-doped layered quaternary compound Nd[O1-xFx]FeAs
• Thorium-doping induced superconductivity up to 56 K in Gd1-xThxFeAsO
• Very High Field Two-Band Superconductivity in LaFeAsO_0.89F_0.11
• Coherence-incoherence crossover in the normal state of iron-oxypnictides and importance of the Hund's rule coupling
• Superconductivity at 52 K in iron-based F-doped layered quaternary compound Pr[O1-xFx]FeAs
• The challenge of unravelling magnetic properties in LaFeAsO
• Electronic structure of the iron-based superconductor LaOFeP
• Electron-Hole Symmetry and Magnetic Coupling in Antiferromagnetic LaOFeAs
• Theory of magnetic excitations in iron-based layered superconductors
• Evolution from Itinerant Antiferromagnet to Unconventional Superconductor with Fluorine Doping in La(O_{1-x}F_{x})FeAs Revealed by ^{75}As and ^{139}La Nuclear Magnetic Resonance
• Commensurate Spin Density Wave in LaOFeAs: A Local Probe Study
• Crystallographic Phase Transition and High-Tc Superconductivity in LaFeAsO:F
• Bandwidth and Fermi surface of Iron-Oxypnictides: covalency and sensitivity to structural changes
• Multiple Nodeless Superconducting Gaps in (Ba0.6K0.4)Fe2As2 Superconductor from Angle-Resolved Photoemission Spectroscopy
• Field and Temperature Dependence of the Superfluid Density in LaO_{1-x}F_xFeAs Superconductors: A Muon Spin Relaxation Study
• Superconductivity at 53.5 K in GdFeAsO1-delta
• A possible ground state and its electronic structure of a mother material (LaOFeAs) of new superconductors
• Superconductivity at 36 K in Gadolinium-arsenide Oxides GdO${}_{1-x}$F${}_x$FeAs
• Ab initio Derivation of Low-energy Model for Iron-Based Superconductors LaFeAsO and LaFePO
• Superconductivity coexisting with phase-separated static magnetic order in (Ba,K)Fe${}_2$As${}_2$, (Sr,Na)Fe${}_2$As${}_2$ and CaFe${}_2$As${}_2$
• 19-F NMR Investigation of Iron-pnictide Superconductor LaFeAsO(0.89)F(0.11)
• Coexistence of magnetic fluctuations and superconductivity in the pnictide high temperature superconductor SmFeAsO${}_{1-x}$F${}_x$ measured by muon spin rotation
• Point-Contact Spectroscopy of Iron-Based Layered Superconductor LaO${}_{0.9}$F${}_{0.1-\delta }$FeAs
• Evidence for Two Gaps and Breakdown of the Uemura Plot in Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ Single Crystals
• Muon-spin rotation studies of SmFeAsO_0.85 and NdFeAsO_0.85 superconductors
• Superconducting Gap and Pseudogap in Iron-Based Layered Superconductor La(O${}_{1-x}$F${}_x$)FeAs
• Spin Ordering in LaOFeAs and Its Suppression in Superconductor LaO0.89F0.11FeAs Probed by Mössbauer Spectroscopy
• Condensation, excitation, pairing, and superfluid density in high-$T_c$ superconductors: magnetic resonance mode as a roton analogue and a possible spin-mediated pairing
• Muon spin relaxation studies of magnetic order and superfluid density in antiferromagnetic NdOFeAs, BaFe2As2 and superconducting (Ba,K)Fe2As2
• Electronic Structure and Electron Correlation in LaFeAsO_{1-x}F_x and LaFePO_{1-x}F_x
• MuSR studies of RE(O,F)FeAs (RE = La, Nd, Ce) and LaOFeP systems: possible incommensurate/stripe magnetism and superfluid density
• Superconductivity in the PbO-type Structure alpha-FeSe
• Pairing strengths for a two orbital model of the Fe-pnictides
• Fermi surface and strong coupling superconductivity in single crystal NdFeAsO_{1-x}F_x
• Raman phonons in ReOFeAs (Re= Sm, La)