Recovery of a Parentlike State in Ba_1−xK_xFe_1.86Co_0.14As₂

Abstract

Superconductivity in doped BaFe2As2 is controlled by the charge of the (FeAs)δ− layers. Adjustment from electron to hole doping in Ba1−xKxFe1.86Co0.14As2 tailors the system from superconductivity to static magnetic order and back to superconductivity. When the charges compensate each other, the magnetic phase similar to BaFe2As2 is recovered. Structural parameters play minor roles in the superconductivity but are important for the highest possible critical temperatures.

Microscopic coexistence of magnetism and superconductivity in charge-compensatedBa1−xKx(Fe

“…As previously reported [25], charge compensated Ba 0.87 K 0.13 Fe 1.86 Co 0.14 As 2 shows the tetragonal to orthorhombic phase transition, but with a reduced orthorhombic distortion compared to BaFe 2 As 2 . To check how this parentlike phase is influenced by increased cobalt and potassium substitution in the charge-compensated state, low-temperature powder diffraction was performed.…”

“…We complement our experimental results with a set of density functional theory calculations aiming to separate the effects of the crystallographic changes and the influence of double substitution onto the electronic structure. This investigation of the electronic phase diagram also continues earlier work on the solid solution Ba 1−z K z Fe 1.86 Co 0.14 As 2 , where we have shown, that a combination of Co and K substitution leads to an effective compensation of hole and electron doping near nominal charge compensation z = 0.14 [25]. This result is in good agreement with photoemission data, showing a rigidband-like filling or depleting of the electronic states near the Fermi level [26].…”

“…[25]. Phase homogeneity and crystal structure parameters were determined by Rietveld refinements of x-ray powder patterns collected on a Huber G670 diffractometer with Co-K α1 or Cu-K α1 radiation, equipped with a closed cycle He cryostat.…”

Superconductivity by rare earth doping in the 1038-type compounds (Ca1−xREx)Stürzer1, Derondeau2, Bertschler3 et al. 2015Solid State CommunicationsSelf Cite122210View full textAdd to dashboardCite

“…The optimal electron doping level of 0.13e À /FeAs is comparable to the 1111-superconductors La(O 1À x F x ) FeAs (x¼0.11) [1] and Sm(O 1À x F x )FeAs (x¼0.1) [19]. The comparison with directly electron doped materials like Ba(Fe 1À x Co x ) 2 As 2 appears not meaningful, since the extend of influence of chemical modification inside the FeAs-layer is still not fully understood [20,21].…”

Antiferromagnetic order in CaK(Fe1−xNix)4As4 and its interplay with s

“…From this perspective of electron count, stoichiometric CaKFe 4 As 4 may be viewed as nearly optimally hole-doped CaFe 2 As 2 , but without disorder arising from Ca and K randomly occupying the same site. Partial substitution of Co or Ni for Fe in CaKFe 4 As 4 (electron doping) should, in principle, shift the ground state from superconducting to antiferromagnetically (AFM) ordered [9]. Indeed, superconductivity is suppressed and signatures of an additional phase transition have been observed in electric resistance and specific heat measurements [10].…”