Spin waves and magnetic exchange interactions in insulating Rb0.89Fe1.58Se2

Abstract

The parent compounds of iron pnictide superconductors are bad metals with a collinear antiferromagnetic structure and N é el temperatures below 220 K. Although alkaline iron selenide A y Fe 1.6 + x Se 2 ( A = K, Rb, Cs) superconductors are isostructural with iron pnictides, in the vicinity of the undoped limit they are insulators, forming a block antiferromagnetic order and having N é el temperatures of roughly 500 K. Here we show that the spin waves of the insulating antiferromagnet Rb 0.89 Fe 1.58 Se 2 can be accurately described by a local moment Heisenberg Hamiltonian. A fi tting analysis of the spin wave spectra reveals that the next-nearest neighbour couplings in Rb 0.89 Fe 1.58 Se 2 , (Ba,Ca,Sr)Fe 2 As 2 , and Fe 1.05 Te are of similar magnitude. Our results suggest a common origin for the magnetism of all the Fe-based superconductors, despite having different ground states and antiferromagnetic orderings.

Superconductivity at the border of electron localization and itinerancy

“…For the vacancy-ordered parent insulating system (the so-called 245 phase), it causes the electronic excitations to have a large incoherent component; the latter gives rise to a large spin spectral weight even in the absence of any itinerant carriers, as have been observed by neutron-scattering experiments 15,16 .…”

“…Inelastic neutron-scattering experiments have shown that the exchange interactions in the alkaline iron selenides and iron pnictides have the same order of magnitude 16 . Further, as Fig.…”

“…We also note that an extended J 1 -J 2 model 16,45 , with ferromagnetic n.n. coupling, defined on a modulated square lattice, has been used to explain the ffiffi ffi 5 p  ffiffi ffi 5 p block spin anti-ferromagnetic order.…”

Robustness ofs-Wave Pairing in Electron-OverdopedA1−yFe2−xSe2Fang1, Wu2, Thomale3 et al. 2011Phys. Rev. XSelf Cite9751141View full textAdd to dashboardCite

“…In this paper, we predict that the s-wave pairing symmetry is robust even in highly electron-overdoped iron chalcogenides because the AFM J 2 is the main factor for pairing, and the J 1 is assumed to be ferromagnetic (FM), a hypothesis supported by both neutron-scattering experiments [47][48][49][50] and the magnetic structure associated with 245 vacancy ordering [51,52]. (''245 vacancy pairing'' is the ordering of vacancies of iron atoms into a certain pattern observed in stoichiometric A 0:8 Fe 1:6 As 2 , where A is an alkaline metal.)…”

Understanding Doping, Vacancy, Lattice Stability, and Superconductivity in KxFe2−ySe2

“…In comparison to the iron pnictides, metal‐intercalated iron selenides are much more complicated in terms of structure, chemical composition, and phases. The nature of the superconducting (SC) phase, for example, is still in debate though considerable progress has been made over the last few years 14, 15, 16…”