Onari and Kontani Reply:

Onari, Seiichiro; Kontani, Hiroshi

doi:10.1103/physrevlett.106.259702

Cited by 328 publications

(851 citation statements)

References 7 publications

(15 reference statements)

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“…If the peak is due to the coherence factor effect characterizing the superconducting condensed state with the S ± symmetry, the peak position E p is expected to be smaller than the value |∆ Γ |+|∆ M |, where ∆ Γ and ∆ M are superconducting order parameters on the Fermi surfaces around Γ and M points, respectively [15]. Here, judging from the experimental values of the ∆ values observed for various systems, the observed value of E p /k B T c (> 6) can hardly be considered to satisfy the condition E p < |∆ Γ |+|∆ M |, indicating that the peak is not due to the effect of coherence factor of the S ± symmetry, but probably due to a different effect predicted for the S ++ symmetry of ∆ by Onari et al [16]. Additionally, we have found the rather large difference of the Q-scan profile widths (δQ) of the magnetic excitation between ω = 5 meV and 7 meV from the data at T = 90 K. The δQ with ω = 5 meV is broader than one with ω = 7 meV.…”

Section: T Dependence Of the Dynamical Magnetic Susceptibility Acrossmentioning

confidence: 76%

“…From the relations T N < T s < T * , we presume that the observed structural transition is related to ordering of 3d yz and 3d zx orbitals and that the C 4 symmetry breaking can be understood as a kind of precursor of this ordering, because the fluctuation (electron-occupancy fluctuation) between these orbitals or their ordering is naturally expected to couple to the orthorhombic distortion. On this point, it has been pointed out theoretically [2,3] that the orbital fluctuation is strong at around both Γ and M points of the (pseudo) tetragonal lattice in the reciprocal space, implying that evidence for the strong effects of the fluctuations on dynamical properties of lattice system can be found experimentally. Thus, we consider that in the phase diagram all the spins, orbitals, lattices, and couplings among these freedoms are involved as important ingredients.…”

Section: Introductionmentioning

confidence: 98%

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Phonons and Spin Excitations in Fe-Based Superconductor Ca₁₀Pt₄As₈ (Fe₁₋_xPt_xAs)₁₀ (x ∼ 0.2)

Ikeuchi¹,

Sato²,

Kajimoto³

et al. 2014

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013)

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By means of neutron inelastic scattering, magnetic excitations and phonons were measured for a single crystal of slightly overdoped superconductor Ca 10 Pt 4 As 8 (Fe 1−x Pt x As) 10 (x ∼ 0.2) with the transition temperature T c of ∼33 K. Below T c , magnetic excitation spectra χ"(Q, ω) measured at Q = Q M [magnetic Γ points] are gapped, and in the relatively higher ω region, the χ"(Q M , ω)-increase was observed with decreasing T , where the maximum of the increase was found at ∼18 meV at 3 K (<< T c ). These characteristics are favorable to orbital-fluctuation-mediated superconductivity with the so-called S ++ symmetry of the order parameter. The energy dependence of δQ-temperature(T ) curve of the magnetic excitations seems to have anomalous behavior in rather wide T region above T c , δQ being the width of the Q scan profile. In the phonon measurements, we observed softening of the in-plane TA mode, which corresponds to the elastic constant C 66 . This softening seems to start at rather high temperature T , as T is lowered. Additionally, anomalous increase in spectral weights of the TO-phonons at around Q M in the region 35 < ω < 40 meV was found even above T c , as T is lowered from ambient T . Because the spectral weights in this ω region mainly correspond to the in-plane motions of Fe atoms and because orbital fluctuations are expected to be strong at around Q M , the result may present clues to investigate a possible coupling between the fluctuations of the orbitals and lattice system.

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Section: T Dependence Of the Dynamical Magnetic Susceptibility Acrossmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 98%

Phonons and Spin Excitations in Fe-Based Superconductor Ca₁₀Pt₄As₈ (Fe₁₋_xPt_xAs)₁₀ (x ∼ 0.2)

Ikeuchi¹,

Sato²,

Kajimoto³

et al. 2014

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013)

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“…For instance, vertex correction due to Aslamazov-Larkin terms which is not included in the RPA plays an important role to stabilize the s ++ -wave state in ironpnictides. 4 Therefore, it is an important issue to investigate the role of higher order corrections.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…The most of the 1111 and the 122 systems show the tetragonal-orthorhombic structural transition and the stripetype antiferromagnetic (AFM) transition. Corresponding to the structural and the AFM transitions, two distinct s-wave pairings: the s ± -wave state with sign change of the gap function ∆(k) between the hole and the electron Fermi surfaces (FSs) mediated by the antiferromagnetic fluctuation 2,3 and the s ++ -wave state without the sign change mediated by the ferro-orbital (FO) fluctuation, which is responsible for the softening of C 66 through the mode-coupling correction 4 or the electron-phonon coupling, 5 and/or the antiferro-orbital (AFO) fluctuation 6,7 were proposed.…”

Section: Introductionmentioning

confidence: 99%

Hole-s_± State Induced by Coexisting Ferro- and Antiferromagnetic and Antiferro-orbital Fluctuations in Iron Pnictides

et al. 2016

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The multi-orbital Hubbard model is investigated in order to clarify the electron correlation effects and the superconductivity in the iron-based superconductor. The renormalization effects on the self-energy and the two-particle irreducible vertex function are calculated on the basis of the dynamical mean field theory. We find that the vertex function exhibits a strong renormalization with the significant orbital dependence as compared with the renormalization factor, when the antiferromagnetic and the antiferro-orbital fluctuations are comparably enhanced due to the electron and the hole Fermi surfaces nesting effects. The orbital-dependent vertex function together with the q ∼ 0 nesting between the two-hole Fermi surfaces results in the inter-orbital ferromagnetic fluctuation gradually enhanced which is expected to be observed in LiFeAs. We show that the hole-s±-wave superconductivity with the sign change of the two-hole Fermi surfaces is realized by the enhanced ferromagnetic fluctuation accompanied by the antiferromagnetic fluctuation and the antiferro-orbital fluctuation.

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“…On the other hand, it has been proposed that s ++ -wave order, where the two signs are the same, emerges when orbital fluctuation is responsible for superconductivity. 3,4 s +− and s ++ are possible candidates of SC symmetry in iron-based superconductors.…”

Section: Introductionmentioning

confidence: 99%

Coexistence of Antiferromagnetism and Superconductivity in Iron-Based Superconductors

2014

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We theoretically investigate the coexistence of antiferromagnetism and superconductivity in the iron-based superconductors by using the mean-field theory for two-and three-orbital models. We find that both the s+−-wave and s++-wave superconductivity can coexist with antiferromagnetism in the two models. On Dirac Fermi surfaces emerging in the antiferromagnetic phase, a superconducting-gap function has a node for s++ wave but is nodeless for s+− wave. On the other hand, the gap function on non-Dirac Fermi surfaces is either nodeless or accidentally nodal, depending on the parameters of pairing interaction, which is independent of pairing symmetry. IntroductionUnderstanding the phase diagram of iron-based superconductors is a key to clarify the physics of superconductivity of these systems. Parent compounds of iron-based superconductors show an antiferromagnetic (AFM) spin density wave (SDW) below a Néel temperature. With hole or electron doping, magnetization is suppressed and superconductivity emerges. A close relationship of AFM and superconducting (SC) phases indicates that the formation of a Cooper pair is mediated by spin fluctuation, which leads to s +− -wave order 1, 2 where the sign of the gap function on hole Fermi surfaces (FSs) centered at the momentum k = (0, 0) is opposite to that on electron FSs at k=(π,0) and (0,π). On the other hand, it has been proposed that s ++ -wave order, where the two signs are the same, emerges when orbital fluctuation is responsible for superconductivity. 3, 4 s +− and s ++ are possible candidates of SC symmetry in iron-based superconductors.Since the AFM and SC phases are next to each other, the boundary of the two phases may provide useful information on superconductivity of iron-based superconductors. Intriguingly, Ba 1−x K x Fe 2 As 2 , Ba(Fe 1−x Co x ) 2 As 2 and BaFe 2 (As 1−x P x ) 2 show a microscopically coexisting phase of AFM and SC orders, supported by neutron diffraction, 5, 6 X-ray diffraction, 5, 7-9 and NMR 10, 11 experiments.Such a coexistence phase has theoretically been investigated, 12-17 where it is commonly assumed that FSs in a paramagnetic phase consists of a near-circular hole pocket centered at k = (0, 0) and an elliptical electron pocket at k=(π,0) and (0,π). The AFM order with wave vector Q=(π,0) mixes the hole and electron dispersions and a SDW gap is open. Resulting reconstructed FS is completely different from the FS of original paramagnetic phase. In the coexistence phase, it has been pointed out that the SC-gap function on the newly reconstructed

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Onari and Kontani Reply:

Cited by 328 publications

References 7 publications

Phonons and Spin Excitations in Fe-Based Superconductor Ca₁₀Pt₄As₈ (Fe₁₋_xPt_xAs)₁₀ (x ∼ 0.2)

Phonons and Spin Excitations in Fe-Based Superconductor Ca₁₀Pt₄As₈ (Fe₁₋_xPt_xAs)₁₀ (x ∼ 0.2)

Hole-s_± State Induced by Coexisting Ferro- and Antiferromagnetic and Antiferro-orbital Fluctuations in Iron Pnictides

Coexistence of Antiferromagnetism and Superconductivity in Iron-Based Superconductors

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Onari and Kontani Reply:

Cited by 328 publications

References 7 publications

Phonons and Spin Excitations in Fe-Based Superconductor Ca10Pt4As8 (Fe1−xPtxAs)10 (x ∼ 0.2)

Phonons and Spin Excitations in Fe-Based Superconductor Ca10Pt4As8 (Fe1−xPtxAs)10 (x ∼ 0.2)

Hole-s± State Induced by Coexisting Ferro- and Antiferromagnetic and Antiferro-orbital Fluctuations in Iron Pnictides

Coexistence of Antiferromagnetism and Superconductivity in Iron-Based Superconductors

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Product

Resources

About

Phonons and Spin Excitations in Fe-Based Superconductor Ca₁₀Pt₄As₈ (Fe₁₋_xPt_xAs)₁₀ (x ∼ 0.2)

Phonons and Spin Excitations in Fe-Based Superconductor Ca₁₀Pt₄As₈ (Fe₁₋_xPt_xAs)₁₀ (x ∼ 0.2)

Hole-s_± State Induced by Coexisting Ferro- and Antiferromagnetic and Antiferro-orbital Fluctuations in Iron Pnictides