Revealing the dual nature of magnetism in iron pnictides and iron chalcogenides using x-ray emission spectroscopy

Gretarsson, H.; Lupascu, A.; Kim, Jungho; Casa, D.; Gog, T.; Wu, Weixing; Julian, S. R.; Xu, Zhijun; Wen, Jinsheng; Gu, Genda; Yuan, R. H.; Chen, Z. G.; Wang, N.-L.; Khim, Seunghyun; Kim, K. H.; Ishikado, M.; Jarrige, Ignace; Shamoto, S.; Hu, Jin; Fisher, I. R.; Kim, Yong Baek

doi:10.1103/physrevb.84.100509

Cited by 123 publications

(110 citation statements)

References 47 publications

(50 reference statements)

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“…The moments detected by core level photoemission spectroscopy (PES) [158] and x-ray emission spectroscopy (XES) [157] are larger than those measured by INS. However the different results of these techniques suggest fast fluctuations of the atomic spin, beyond the localised model [148].…”

Section: B Antiferromagnetism From Localised Spinsmentioning

confidence: 89%

“…Inelastic neutron scattering (INS) and X-ray experiments have detected spin waves up to energies above 200 meV [7,[153][154][155], larger than predicted by weak coupling approaches [156] and estimated total moments larger than those expected in the weak coupling model [3,7,136,148,157,158] which do not seem to change much with increasing temperatures up to T ∼ 2T N , well above the Néel temperature. This magnetic moment is not only large in systems with magnetic order, but also in compounds which do not order magnetically as LiFeAs or Ba 0.6 K 0.4 Fe 2 As 2 [148].…”

Section: A Weak Coupling Description Of Magnetismmentioning

confidence: 99%

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Magnetic interactions in iron superconductors: A review

Bascones

Valenzuela

Calderón

2015

Comptes Rendus. Physique

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High temperature superconductivity in iron pnictides and chalcogenides emerges when a magnetic phase is suppressed. The multi-orbital character and the strength of correlations underlie this complex phenomenology, involving magnetic softness and anisotropies, with Hund's coupling playing an important role. We review here the different theoretical approaches used to describe the magnetic interactions in these systems. We show that taking into account the orbital degree of freedom allows us to unify in a single phase diagram the main mechanisms proposed to explain the (π, 0) order in iron pnictides: the nesting-driven, the exchange between localized spins, and the Hund induced magnetic state with orbital differentiation. Comparison of theoretical estimates and experimental results helps locate the Fe superconductors in the phase diagram. In addition, orbital physics is crucial to address the magnetic softness, the doping dependent properties, and the anisotropies.

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Section: B Antiferromagnetism From Localised Spinsmentioning

confidence: 89%

Section: A Weak Coupling Description Of Magnetismmentioning

confidence: 99%

Magnetic interactions in iron superconductors: A review

Bascones

Valenzuela

Calderón

2015

Comptes Rendus. Physique

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“…This is much smaller than the spin moment of 4.9 m B expected in the magnetic state of a free Fe 2 þ ion. The exact numbers of local moments of magnetic defects inside the iron-pnictide materials are difficult to estimate, but recent X-ray emission spectroscopy measurements revealed that the instantaneous local moments in various iron pnictides are always about 1 m B per Fe, and for the BaFe 2 As 2 case B1.3 m B per Fe has been found 39 . Thus it is expected that the moment of the order of 1 m B per defect would appear if the defects act as magnetic impurities, which can be ruled out by our results of the lack of a Curie upturn within the B0.2 m B resolution.…”

Section: Resultsmentioning

confidence: 99%

Disorder-induced topological change of the superconducting gap structure in iron pnictides

et al. 2014

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In superconductors with unconventional pairing mechanisms, the energy gap in the excitation spectrum often has nodes, which allow quasiparticle excitations at low energies. In many cases, such as in d-wave cuprate superconductors, the position and topology of nodes are imposed by the symmetry, and thus the presence of gapless excitations is protected against disorder. Here we report on the observation of distinct changes in the gap structure of ironpnictide superconductors with increasing impurity scattering. By the successive introduction of nonmagnetic point defects into BaFe 2 (As 1 À x P x ) 2 crystals via electron irradiation, we find from the low-temperature penetration depth measurements that the nodal state changes to a nodeless state with fully gapped excitations. Moreover, under further irradiation the gapped state evolves into another gapless state, providing bulk evidence of unconventional sign-changing s-wave superconductivity. This demonstrates that the topology of the superconducting gap can be controlled by disorder, which is a strikingly unique feature of iron pnictides.

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“…Early considerations based on Fermi surface nesting provided a robust starting point to rationalize their properties. However, the effect of repulsion between electrons cannot be neglected [6] as exemplified by the existence of large magnetic moments at room temperature [8,9], superconducting materials without hole pockets [10], as well as unexpectedly complex spin arrangements [7]. Electronic correlation effects must be incorporated to understand the plethora of challenging results that experiments are rapidly unveiling.…”

Section: Introductionmentioning

confidence: 99%

Pairing tendencies in a two-orbital Hubbard model in one dimension

et al. 2017

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The recent discovery of superconductivity under high pressure in the ladder compound BaFe2S3 has opened a new field of research in iron-based superconductors with focus on quasi one-dimensional geometries. In this publication, using the Density Matrix Renormalization Group technique, we study a two-orbital Hubbard model defined in one dimensional chains. Our main result is the presence of hole binding tendencies at intermediate Hubbard U repulsion and robust Hund coupling JH /U = 0.25. Binding does not occur neither in weak coupling nor at very strong coupling. The pair-pair correlations that are dominant near half-filling, or of similar strength as the charge and spin correlation channels, involve hole-pair operators that are spin singlets, use nearest-neighbor sites, and employ different orbitals for each hole. The Hund coupling strength, presence of robust magnetic moments, and antiferromagnetic correlations among them are important for the binding tendencies found here.

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Revealing the dual nature of magnetism in iron pnictides and iron chalcogenides using x-ray emission spectroscopy

Cited by 123 publications

References 47 publications

Magnetic interactions in iron superconductors: A review

Magnetic interactions in iron superconductors: A review

Disorder-induced topological change of the superconducting gap structure in iron pnictides

Pairing tendencies in a two-orbital Hubbard model in one dimension

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