Neutron Scattering Study of Magnetic Excitation Spectra of Ba(Fe0.9Co0.1)2As2

Tatematsu, Shunichi; Yasui, Yukihiko; Moyoshi, Taketo; Motoya, Kiyoichiro; Kakurai, Kazuhisa; Sato, Masatoshi

doi:10.1143/jpsj.80.073703

Cited by 12 publications

(5 citation statements)

References 25 publications

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“…To distinguish between these two SC gap states, various phase-sensitive experiments had been performed [18][19][20][21][22][23][24][25]. For example, inelastic neutron scattering experiments had been performed to find the magnetic resonance scattering due to the sign reversal [19][20][21]. However, observed "resonance-like" hump structure can be explained even if s ++ -wave state is realized [26].…”

Section: Introductionmentioning

confidence: 99%

Effect of realistic finite-size impurities onTcin Fe-based superconductors based on the five-orbital tight-binding model

2013

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We present a systematic study of the impurity effect on Tc in Fe-based superconductors, assuming that the sign-reversal s-wave state due to inter-pocket repulsion (s±-wave state) is realized. For this purpose, we introduce several realistic impurity models with non-local modifications of potentials and hopping integrals around the impurity site. When we use the impurity model parameters for 3d-and 4d-impurity atoms derived from the recent first principle study by Nakamura et al., we find that the s±-wave state is very fragile against impurities: The superconductivity without impurities Tc0 = 30K is destroyed by introducing small residual resistivity ρ cr 0 = 5z −1 ∼ 10z −1 [µΩcm] (z −1 = m * /m being the mass-enhancement factor), consistently with the previous theoretical study for the on-site impurity model by Onari and Kontani. This result is essentially unchanged for different non-local impurity models with realistic parameters. We also discuss the effect of the impurity-induced non-local orbital order on the superconducting state.

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Section: Introductionmentioning

confidence: 99%

Effect of realistic finite-size impurities onTcin Fe-based superconductors based on the five-orbital tight-binding model

2013

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“…(∆ is the amplitude of the gap function.) Experimentally, clear broad peak structures in χ S (q, ω) were observed for T ≪ T c in FeSe [33], BaFe 2−x Co x As 2 [34,35], Ca-Fe-Pt-As [36], Na(Fe,Co)As [37], and (Ba,K)Fe 2 As 2 [38]. However, χ S (q, ω) is drastically modified by not only the coherence factor, but also by the self-energy effect.…”

Section: Introductionmentioning

confidence: 99%

Self-energy driven resonancelike inelastic neutron spectrum in the s++ -wave state in Fe-based superconductors

2018

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To elucidate the pairing states in Fe-based superconductors, we perform careful calculation of the dynamical spin susceptibility χ S (q, ω) at very low temperatures (T > ∼ 1meV). The feedback effect on both the self-energy and χ S (q, ω) from the superconducting gap are self-consistently analyzed based on the fluctuation-exchange (FLEX) approximation. In the s±-wave state, which has sign-reversal in the gap function, χ S (q, ω) at the nesting momentum q = Q shows a resonance peak even when the system is away from the magnetic quantum-critical-point (QCP). In the s++-wave state that has no sign-reversal, χ S (q, ω) shows a large hump structure when the system is close to the magnetic QCP. This result confirms the validity of self-energy driven resonance-like peak in s++-wave state proposed in our previous semi-microscopic study: The enhancement in χ S (q, ω) due to self-energy effect exceeds the suppression due to coherence factor effect near magnetic QCP. We stress that the hump structure in the s++-wave state given by the FLEX method smoothly changes to resonancelike sharp peak structure as the system approaches magnetic QCP, which was not reported in our previous studies. The obtained ω-and T -dependences of χ S (q, ω) in the s++-wave state resemble to the resonance-like feature in inelastic neutron scattering spectra recently observed in Na(Fe,Co)As and FeSe.

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“…We have adopted three physical quantities sensitive to the sign reversal of , doping effects of nonmagnetic impurities on T c [7,8], magnetic excitation spectra "(Q, ) [9,10] and the temperature(T) dependence of the NMR longitudinal relaxation rate 1/T 1 [7,11,12], and we have also investigated phonon behavior by neutron scattering measurements, expecting that roles of orbital fluctuations can be found through the orbit-lattice coupling.…”

Section: Introductionmentioning

confidence: 99%

On the Superconducting Symmetry of Fe-Based Systems —Impurity Effects and Microscopic Magnetic Behavior—

Sato¹,

Ikeuchi²,

Kajimoto³

et al. 2014

Proceedings of the 12th Asia Pacific Physics Conference (APPC12)

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To identify the superconducting mechanism of Fe-based systems, we have studied, using several systems, their three physical quantities sensitive to the sign reversal between the superconducting order parameters  on the disconnected Fermi-surfaces around  and M points in the reciprocal space, effects of nonmagnetic impurities on the superconducting transition temperature T c , magnetic excitation spectra and NMR longitudinal relaxation rates 1/T 1 , because the nonexistence(existence) of the sign reversal seems to directly correspond to a new(already known) mechanism of the Cooper pair formation. Encouraged by results of the studies suggesting a new pairing mechanism, we are searching for experimental evidence that the orbital fluctuations (fluctuations of electron-occupancies among 3d orbitals) are playing important roles in the Cooper-pair formation, expecting that it appears through the coupling of the fluctuations with the lattice system. We have carried out neutron measurements of phonons using two single crystals of Ca 10 Pt 4 As 8 (Fe 1-x Pt x As) 10 with pseudo tetragonal structure, and found the softening of the in-plane TA phonons corresponding to the softening of the elastic constant C 66 with decreasing temperature and anomalous T dependence of the phonon spectral weights of in-plane optical modes at the M points. These findings are suggestive of the relevance of orbital fluctuations to the superconducting mechanism, because they are strong at the and M points.

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Neutron Scattering Study of Magnetic Excitation Spectra of Ba(Fe_0.9Co_0.1)₂As₂

Cited by 12 publications

References 25 publications

Effect of realistic finite-size impurities onTcin Fe-based superconductors based on the five-orbital tight-binding model

Effect of realistic finite-size impurities onTcin Fe-based superconductors based on the five-orbital tight-binding model

Self-energy driven resonancelike inelastic neutron spectrum in the s++ -wave state in Fe-based superconductors

On the Superconducting Symmetry of Fe-Based Systems —Impurity Effects and Microscopic Magnetic Behavior—

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