Robust upward dispersion of the neutron spin resonance in the heavy fermion superconductor Ce1−xYbxCoIn5

Song, Yu; Dyke, John S. Van; Lum, I. K.; White, B. D.; Jang, Sooyoung; Yazici, D.; Shu, Lei; Schneidewind, A.; Čermák, P.; Qiu, Yiming; Maple, M. B.; Morr, Dirk K.; Dai, Pengcheng

doi:10.1038/ncomms12774

Cited by 37 publications

(43 citation statements)

References 54 publications

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“…While E 0 depends weakly on temperature, γ increases significantly with increasing temperature. Interestingly, the above analysis indicates that the appearance of the resonance mode in NaFe 0.9785 Co 0.0215 As can be interpreted as removal of damping from an existing mode, a scenario recently proposed for Ce 1−x Yb x CoIn 5 [50]. However, we note that unlike Ce 1−x Yb x CoIn 5 , behaviors of the resonance mode in iron pnictides are also consistent with the spin-exciton scenario [27,51].…”

Section: A Temperature Dependence Of Spin Fluctuations From Unpolarimentioning

confidence: 63%

Temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As

et al. 2017

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We use unpolarized and polarized neutron scattering to study the temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe 0.9785 Co 0.0215 As, with coexisting superconductivity (T c ≈ 19 K) and weak antiferromagnetic order (T N ≈ 30 K, ordered moment ≈0.02 μ B /Fe). A single spin resonance mode with intensity tracking the superconducting order parameter is observed, although energy of the mode only softens slightly upon approaching T c . Polarized neutron scattering reveals that the single resonance is mostly isotropic in spin space, similar to overdoped NaFe 0.935 Co 0.045 As but different from optimal electron-, hole-, and isovalently doped BaFe 2 As 2 compounds, all featuring an additional prominent anisotropic component. Spin anisotropy in NaFe 0.9785 Co 0.0215 As is instead present at energies below the resonance, which becomes partially gapped below T c , similar to the situation in optimally doped YBa 2 Cu 3 O 6.9 . Our results indicate that anisotropic spin fluctuations in NaFe 1−x Co x As appear in the form of a resonance in the underdoped regime, become partially gapped below T c near optimal doping, and disappear in overdoped compounds.

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Section: A Temperature Dependence Of Spin Fluctuations From Unpolarimentioning

confidence: 63%

Temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As

et al. 2017

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“…As discussed above in 2.1.3., such a resonance would normally be considered to be evidence for a sign change in the superconducting energy gap  on different parts of the Fermi surface, as would be consistent with the d-wave pairing symmetry already implied from numerous measurements discussed here. However, recent neutron scattering data (Song et al [232]) on Ce1-xYbxCoIn5, x=0, 0.05, and 0.3, have called this interpretation of the observed resonance in CeCoIn5 into question. Rather than being due to a spin exciton that implies a sign change of the gap function (d or s± symmetry), Song et al describe the observed resonance as being due to a magnon-like excitation, with no implication about a sign change in (k).…”

Section: Cecoin5mentioning

confidence: 99%

Unconventional superconductivity

Stewart

2017

Advances in Physics

221

165

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Abstract:"Conventional" superconductivity, as used in this review, refers to electron-phonon coupled superconducting electron pairs described by BCS theory. Unconventional superconductivity refers to superconductors where the Cooper pairs are not bound together by phonon-exchange but instead by exchange of some other kind, e. g. spin fluctuations in a superconductor with magnetic order either coexistent or nearby in the phase diagram. Such unconventional superconductivity has been known experimentally since heavy fermion CeCu2Si2, with its strongly correlated 4f electrons, was discovered to superconduct below 0.6 K in 1979. Since the discovery of unconventional superconductivity in the layered cuprates in 1986, the study of these materials saw Tc jump to 164 K by 1994. Further progess in high temperature superconductivity would be aided by understanding the cause of such unconventional pairing. This review compares the fundamental properties of 9 unconventional superconducting classes of materialsfrom 4f-electron heavy fermions to organic superconductors to classes where only three known members exist to the cuprates with over 200 examples -with the hope that common features will emerge to help theory explain (and predict!) these phenomena. In addition, three new emerging classes of superconductors (topological, interfacial -e. g. FeSe on SrTiO3, and H2S under high pressure) are briefly covered, even though their "conventionality" is not yet fully determined.

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“…For heavy-fermion compounds, spin excitation energies are about two orders of magnitude smaller than for cuprates and pnictides, in agreement with the difference in characteristic temperatures, and can thus be conveniently measured by INS. Among the heavy-fermion superconductors close to a magnetic QCP, dispersive excitations have been reported for CePt 3 Si [20], CeCoIn 5 [21,22], and CeCu 2 Si 2 [23,24]. In CePt 3 Si [20], magnetism and superconductivity coexist at low temperatures and no difference was found for the magnetic excitations of the purely magnetic and the mixed magneticsuperconducting state.…”

Section: Different Classes Of Unconventional Superconductorshigh-t Cmentioning

confidence: 99%

Robustness of magnons near the quantum critical point in the heavy-fermion superconductor CeCu2Si2

Huesges

Schmalzl²,

Geibel

et al. 2018

Phys. Rev. B

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Paramagnons are supposed to provide the pairing glue for unconventional superconductors. For the heavyfermion superconductor CeCu 2 Si 2 , there is indeed good evidence from inelastic neutron scattering (INS) that spin fluctuations drive the superconductivity. Here, we present the INS measurement of the inelastic response of the antiferromagnetic parent compound, 'A-type' CeCu 2 Si 2 , to probe the relation to the excitations of the superconducting ('S-type') sample. We find that the dispersion is very similar in the antiferromagnetic state and in the normal state of the superconducting sample. Pronounced differences to the response in the superconducting state exist at low energies around the zone center. These findings are in line with observations of other unconventional superconductors.

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Robust upward dispersion of the neutron spin resonance in the heavy fermion superconductor Ce1−xYbxCoIn5

Cited by 37 publications

References 54 publications

Temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As

Temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As

Unconventional superconductivity

Robustness of magnons near the quantum critical point in the heavy-fermion superconductor CeCu2Si2

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