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Okazaki, Kozo; Sugai, S.; Niitaka, Seiji; Takagi, H.

doi:10.1103/physrevb.83.035103

Cited by 49 publications

(57 citation statements)

References 54 publications

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“…As noted previously in a high-energy neutron scattering study [61], as a function of interstitial iron concentration, the magnetic excitations extend up to ∼200 meV, and this is also confirmed by two-magnon results using Raman [66]. Within an error of ±15 %, we observe no temperature dependence of the integrated intensity at 5, 70, and 100 K, integrating over energy transfers up to 50 meV.…”

Section: X = 0057(7): Collinear Magnetism and Stripy Fluctuationssupporting

confidence: 66%

Competing spin density wave, collinear, and helical magnetism inFe1+xTe

et al. 2017

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The Fe 1+x Te phase diagram consists of two distinct magnetic structures with collinear order present at low interstitial iron concentrations and a helical phase at large values of x with these phases separated by a Lifshitz point. We use unpolarized single-crystal diffraction to confirm the helical phase for large interstitial iron concentrations and polarized single-crystal diffraction to demonstrate the collinear order for the iron-deficient side of the Fe 1+x Te phase diagram. Polarized neutron inelastic scattering shows that the fluctuations associated with this collinear order are predominately transverse at low-energy transfers, consistent with a localized magnetic moment picture. We then apply neutron inelastic scattering and polarization analysis to investigate the dynamics and structure near the boundary between collinear and helical orders in the Fe 1+x Te phase diagram. We first show that the phase separating collinear and helical orders is characterized by a spin density wave with a single propagation wave vector of (∼0.45, 0, 0.5). We do not observe harmonics or the presence of a charge density wave. The magnetic fluctuations associated with this wave vector are different from the collinear phase, being strongly longitudinal in nature and correlated anisotropically in the (H,K) plane. The excitations preserve the C 4 symmetry of the lattice but display different widths in momentum along the two tetragonal directions at low-energy transfers. While the low-energy excitations and minimal magnetic phase diagram can be understood in terms of localized interactions, we suggest that the presence of the density wave phase implies the importance of electronic and orbital properties.

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Section: X = 0057(7): Collinear Magnetism and Stripy Fluctuationssupporting

confidence: 66%

Competing spin density wave, collinear, and helical magnetism inFe1+xTe

et al. 2017

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“…However, the lost spin order is only perpendicular to the two-dimensional layer 7 and the high-energy magnetic excitations in the layer clearly remains above T SDW or in the metallic phase as observed in magnetic Raman scattering and neutron scattering. [8][9][10][11][12] It strongly suggests that the superconductivity is induced by the same magnetic correlation as in the SDW state.…”

Section: Introductionmentioning

confidence: 99%

Spin-Density-Wave Gap with Dirac Nodes and Two-Magnon Raman Scattering in BaFe₂As₂

et al. 2012

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Journal of the Physical Society of Japan FULL PAPERSRaman selection rules for electronic and magnetic excitations in BaFe 2 As 2 were theoretically investigated and applied them to the separate detection of the nodal and anti-nodal gap excitations at the spin density wave (SDW) transition and the separate detection of the nearest and the next nearest neighbor exchange interaction energies.Raman spectra are composed of magnetic excitations with gradually decreasing intensity toward far above the SDW transition temperature (T SDW ) and electronic excitations induced by the Brillouin zone folding below T SDW . The SDW gap has Dirac nodes, be- and change into the gap structure by the first order transition at T SDW , while those from the nodal region gradually change into the SDW state. Magnetic excitations are observed as a very broad peak in all polarization configurations. The selection rule for two-magnon scattering from the stripe spin structure was obtained. Applying it to the two-magnon Raman spectra it is found that the magnetic exchange interaction energies are not presented by the short-range superexchange model, but the second derivative of the total energy of the stripe spin structure with respect to the moment directions.The selection rule and the peak energy are expressed by the two-magnon scattering process in an insulator, but the large spectral weight above twice the maximum spin wave energy is difficult to explain by the decayed spin wave. It may be explained by the electronic scattering of itinerant carriers with the magnetic self-energy in the localized spin picture or the particle-hole excitation model in the itinerant spin picture.The magnetic scattering spectra are compared to the insulating and metallic cuprate superconductors whose spins are believed to be localized.

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“…42 Calculations indicate that A 1g spectra correspond to hole-like Fermi surfaces around  points. Unfortunately, only a slope-like feature rather than a peak is observed due to very weak signal.…”

Section: K Okazaki Et Al Carried Out Electronic Raman Scattering Mementioning

confidence: 99%

“…This may suggest a slight structural change and a weak connection between phonons and SDW/superconductivity. 16,17 Similarly, in LiFeAs ("111") without structural and magnetic transitions, both positions and widths of phonons follow a normal anharmonic trend, which implies a weak electron-and spin-phonon coupling. …”

mentioning

confidence: 99%

Raman Scattering in Iron-Based Superconductors

Zhang

2012

Mod. Phys. Lett. B

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Iron-based superconducting layered compounds have the second highest transition temperature after cuprate superconductors.Their discovery is a milestone in the history of high-temperature superconductivity and will have profound implications for high-temperature superconducting mechanism as well as industrial applications. Raman scattering has been extensively applied to correlated electron systems including the new superconductors due to its unique ability to probe multiple primary excitations and their coupling. In this review, we will give a brief summary of the existing Raman experiments in the iron-based materials and their implication for pairing mechanism in particular. And we will also address some open issues from the experiments.Keywords: Raman scattering; iron-based superconductor; electron-phonon coupling; electronic Raman scattering; two-magnon process. BackgroundRaman scattering, also known as inelastic light scattering, was discovered in 1928 by C. V. Raman. It can be used to detect many kinds of excitations in solids, such as phonons, 1 magnons, 2 excitons 3 etc.With the invention of laser and the continuous improvement of monochromator and new-generation detectors, Raman scattering has become a conventional and fundamental technique in many fields.Superconductivity is one of the most important frontiers in condensed matter physics and much Raman scattering work has been done in the field so far. Basically, Raman scattering can probe phonons and related electron-phonon coupling. The information on superconducting gap size can be drawn from cooper-pair-breaking peak in electronic Raman scattering spectra. Symmetry analysis is a unique advantage of Raman scattering. In a non-isotropic superconductor, the position, shape and low-energy behavior of pair-breaking peak will substantially change in different symmetry channels, which gives a unique way to explore pairing symmetry. Raman scattering has also been employed to detect two-magnon procedure in spin-ordered systems, from which we can obtain accurate exchange energies and learn the evolution of spin fluctuation. Actually, Raman scattering plays a crucial role in the study of cuprate superconductors.Since its discovery in 2008, iron-based superconductor has attracted a lot of interests due to its second highest transition temperature after cuprate superconductor. So far, all known iron-based superconductors can be divided into six categories in structure: 1, "1111", represented by F-doped LaFeAsO, is the first iron-based superconductor. The highest Tc reaches up to 56 K by rare-earth substitution. 4 2, "122", represented by Co or K-doped BaFe 2 As 2 , is the most studied system due to available high-quality crystals and tunable doping levels. 5 3, "111" refers to LiFeAs with the maximum Tc of 18 K. 6 4, "11" is Fe(Se,Te), the prototype of iron-based superconductor without poisonous element As. 7 5, "21311" is isostructural to 122 system with a divalent group instead of Ba. 8 6, A 0.8 Fe 1.6 Fe 2 (A=K, Tl, Cs…), which has ordered Fe-vacancies was d...

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Phonon, two-magnon, and electronic Raman scattering of Fe1+yTe1−xSe
Kozo Okazaki
¹
,
S. Sugai
²
,
Seiji Niitaka
³

et al.

Cited by 49 publications

References 54 publications

Competing spin density wave, collinear, and helical magnetism inFe1+xTe

Competing spin density wave, collinear, and helical magnetism inFe1+xTe

Spin-Density-Wave Gap with Dirac Nodes and Two-Magnon Raman Scattering in BaFe₂As₂

Raman Scattering in Iron-Based Superconductors

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Phonon, two-magnon, and electronic Raman scattering of Fe1+yTe1−xSeKozo Okazaki1, S. Sugai2, Seiji Niitaka3 et al.

Cited by 49 publications

References 54 publications

Competing spin density wave, collinear, and helical magnetism inFe1+xTe

Competing spin density wave, collinear, and helical magnetism inFe1+xTe

Spin-Density-Wave Gap with Dirac Nodes and Two-Magnon Raman Scattering in BaFe2As2

Raman Scattering in Iron-Based Superconductors

Contact Info

Product

Resources

About

Phonon, two-magnon, and electronic Raman scattering of Fe1+yTe1−xSe
Kozo Okazaki
¹
,
S. Sugai
²
,
Seiji Niitaka
³

et al.

Spin-Density-Wave Gap with Dirac Nodes and Two-Magnon Raman Scattering in BaFe₂As₂