Bipartite magnetic parent phases in the iron oxypnictide superconductor

Abstract

High-temperature (high-T c ) superconductivity appears as a consequence of the carrier-doping of an undoped parent compound exhibiting antiferromagnetic order; thereby, ground-state properties of the parent compound are closely relevant to the superconducting state 1,2 . On the basis of the concept, a spin-fluctuation has been addressed as an origin of pairing of the superconducting electrons in cuprates 1 . Whereas, there is growing interest in the pairing mechanism such as an unconventional spin-fluctuation or an advanced orbital-fluctuation due to the characteristic multi-orbital system in iron-pnictides 3-6 . Here, we report the discovery of an antiferromagnetic order as well as a unique structural transition in electron-overdoped

Antiferromagnetic order and spin dynamics in iron-based superconductors

“…1(c)] AF structures, respectively. Recently, another AF parent compound was found in electron-overdoped LaFeAsO 1−x H x (x ∼ 0.5) system in addition to the usual collinear AF structure at x = 0 (Hiraishi et al, 2014).…”

“…For samples with x > 0.9, it becomes heavy fermion-like metal . (c) The structural, magnetic, and superconducting phase transitions in H-doped LaFeAsO1−xHx (Hiraishi et al, 2014). There are two AF phases with different magnetic structures near two superconducting domes.…”

High-TcSuperconductivity near the Anion Height Instability in Fe-Based Superconductors: Analysis ofLaFeAsO1−xOnari1, Yamakawa2, Kontani3 2014Phys. Rev. Lett.70101000View full textAdd to dashboardCite

“…In summary, we studied the phase diagram of LaFeAsO 1−x H x using the SC-VC Σ method, and predicted that the non-nematic O 3z 2 −r 2 order triggers the new C 4 isostructural transition at x ∼ 0.5 [17]. Also, we obtain the approximate s ++ -wave gap structure due to orbital fluctuations for both x 0 and x 0.5 by taking the ∆-VC into account.…”

“…[21] discussed that the C 4 phase in (Ba,Na)Fe 2 As 2 originates from the C 4 magnetic order. However, stripe magnetic order (=C 2 symmetry) is realized in LaFeAsO 1−x H x at x ∼ 0.5 [17], which indicates small spin-lattice coupling. We predict that non-nematic O 3z 2 −r 2 (nematic O x 2 −y 2 ) charge quadrupole order emerges in the C4 (C2) phase.…”

“…The second superconducting dome (x ≥ 0.2) is next to the "C 4 isostructural phase transition" with sizable change in the c-axis length (or anion-height) for 0.45 < x < 0.5 [17,18]. (The c-axis length is unchanged in the C 2 structure transition at x ∼ 0.)…”