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Antiferroic electronic structure in the nonmagnetic superconducting state of the iron-based superconductors

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Science Advances  25 Aug 2017:
Vol. 3, no. 8, e1700466
DOI: 10.1126/sciadv.1700466
  • Fig. 1 Temperature-dependent ARPES around X point for Ba0.59K0.41Fe2As2.

    (A) Phase diagram of BaK122 (2). TN and Ts are nearly equivalent in this system. (B) FSs of OP BaK122 obtained at 40 K with the photons of hν = 21.2 eV. (C) Schematic of (B). (D) E-k image divided by the Fermi-Dirac function taken at 40 K along cut 1 in (C). (E) Peak positions of the EDCs (filled diamonds) and momentum distribution curves (MDCs) (open diamonds) in (D). (F and G) The same as (D) and (E), but obtained at 15 K. (H) T dependence of the peak plots around X point from 15 to 90 K. (I) Schematic of (H). Δe and Ebot represent the SC gap magnitude of the electron band and energy level of the band bottom, respectively. (J and K) T dependence of the EDCs divided by the Fermi-Dirac functions at X point and kF of the electron band (k = 0.06 Å−1), respectively.

  • Fig. 2 Temperature-dependent ARPES around Γ point for Ba0.59K0.41Fe2As2.

    (A to D) T dependence of E-k images divided by the Fermi-Dirac functions obtained by laser-ARPES (hν = 6.994 eV) along cut 2 in Fig. 1C. (E to H) Peak plots obtained from EDCs (filled circles) and MDCs (open circles) in (A) to (D). Gray curves are guides to the eye. Δh and Eflat represent the SC gap magnitude of the inner hole band and the energy level of the flat intensity distribution at kF, respectively. (I) T dependence of the EDCs at kF of inner hole band. (J) The EDCs in (I) divided by the Fermi-Dirac functions and further normalized by that at 60 K. The data set shown in (I) and (J) was taken from Shimojima et al. (28). (K) T dependences in the energy levels of Δh, Δe, Ebot, and Eflat. Black solid curves represent the BCS curves for hole and electron bands.

  • Fig. 3 Schematic of the (π,π) folding.

    (A) Schematic of the (π,π) folding in the BZ for x = 0.41. Folded FSs are indicated in light colors. kX and kY represent the momentum axes with the tetragonal settings. (B) Simplified schematic of the hole and electron bands above Tc for x = 0.41. (C) The same as (B) but far below Tc. Δe and Δh represent the SC gaps of the electron and hole bands, respectively. (D) The same as (C) but in the presence of the (π,π) folding.

  • Fig. 4 x and T dependences of the flat intensity at Γ point.

    (A) E-k images around Γ point in the SC state for x = 0.30, 0.51, and 0.57 obtained by laser-ARPES (hν = 6.994 eV). White circles represent the peak positions of the EDCs corresponding to the flat feature around Γ point. White horizontal lines show the location of the SC peak. (B) x dependence of the EDCs at the kF of the inner hole band. Red and black markers represent the energy levels of the flat feature and SC gap, respectively. (C) Contour plot of the spectral weight derived from the flat feature around Γ point in the x-T phase diagram of the BaK122 system. The spectral weight was integrated between −5 and +5 meV around Eflat in the EDC at kF of the inner hole band (section S5). The measurement points are indicated by black dots.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/8/e1700466/DC1

    section S1. Band dispersions near X point

    section S2. T dependence of the EDCs around X point divided by the Fermi-Dirac function

    section S3. Intensity distribution of the flat feature around Γ point

    section S4. Origin of the flat feature at Γ point

    section S5. Band dispersion at X point for x = 0.51

    section S6. x and T dependences of the EDCs at kF of the inner hole band around Γ point

    section S7. Contributions of the antiferroic instability in the ARPES data

    fig. S1. Band structure across Γ-X line.

    fig. S2. T dependence of the electron band at X point.

    fig. S3. Intensity distribution around Γ point.

    fig. S4. T dependence of the flat feature.

    fig. S5. Band dispersions at Γ and X points for x = 0.51.

    fig. S6. x and T dependences of the flat feature.

    fig. S7. Normalized intensity of the flat feature.

    fig. S8. Spectral intensity ratio between Γ and X points.

  • Supplementary Materials

    This PDF file includes:

    • section S1. Band dispersions near X point
    • section S2. T dependence of the EDCs around X point divided by the Fermi-Dirac function
    • section S3. Intensity distribution of the flat feature around Γ point
    • section S4. Origin of the flat feature at Γ point
    • section S5. Band dispersion at X point for x = 0.51
    • section S6. x and T dependences of the EDCs at kF of the inner hole band around Γ point
    • section S7. Contributions of the antiferroic instability in the ARPES data
    • fig. S1. Band structure across Γ-X line.
    • fig. S2. T dependence of the electron band at X point.
    • fig. S3. Intensity distribution around Γ point.
    • fig. S4. T dependence of the flat feature.
    • fig. S5. Band dispersions at Γ and X points for x = 0.51.
    • fig. S6. x and T dependences of the flat feature.
    • fig. S7. Normalized intensity of the flat feature.
    • fig. S8. Spectral intensity ratio between Γ and X points.

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