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

Yu Song; Weiyi Wang; Chenglin Zhang; Yanhong Gu; Xingye Lu; Guotai Tan; Yixi Su; Frédéric Bourdarot; A. D. Christianson; Shiliang Li; Pengcheng Dai

doi:10.1103/PhysRevB.96.184512

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

Yu Song, Weiyi Wang, Chenglin Zhang, Yanhong Gu, Xingye Lu, Guotai Tan, Yixi Su, Frédéric Bourdarot, A. D. Christianson, Shiliang Li, Pengcheng Dai

Correlated Electron Materials

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Abstract

We use unpolarized and polarized neutron scattering to study the temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As, with coexisting superconductivity (Tc≈19 K) and weak antiferromagnetic order (TN≈30 K, ordered moment ≈0.02μB/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 Tc. Polarized neutron scattering reveals that the single resonance is mostly isotropic in spin space, similar to overdoped NaFe0.935Co0.045As but different from optimal electron-, hole-, and isovalently doped BaFe2As2 compounds, all featuring an additional prominent anisotropic component. Spin anisotropy in NaFe0.9785Co0.0215As is instead present at energies below the resonance, which becomes partially gapped below Tc, similar to the situation in optimally doped YBa2Cu3O6.9. Our results indicate that anisotropic spin fluctuations in NaFe1-xCoxAs appear in the form of a resonance in the underdoped regime, become partially gapped below Tc near optimal doping, and disappear in overdoped compounds.

Original language	English
Article number	184512
Journal	Physical Review B
Volume	96
Issue number	18
DOIs	https://doi.org/10.1103/PhysRevB.96.184512
State	Published - Nov 14 2017

Funding

We thank Zhuang Xu and Huiqian Luo for assistance in resistivity change under uniaxial stress measurements. The single crystal growth and neutron scattering work at Rice is supported by the US DOE, BES, under Contract No. DE-SC0012311 (P.D.). The materials work at Rice is also supported by Robert A. Welch Foundation Grant No. C-1839 (P.D.). The work at IOP is supported by the Ministry of Science and Technology of China (No. 2017YFA0302903, No. 2016YFA0300502), the National Natural Science Foundation of China (No. 11374346, No. 11674406) and the Strategic Priority Research Program(B) of the Chinese Academy of Sciences (XDB07020300). This research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by Oak Ridge National Laboratory.

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

abstract = "We use unpolarized and polarized neutron scattering to study the temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As, with coexisting superconductivity (Tc≈19 K) and weak antiferromagnetic order (TN≈30 K, ordered moment ≈0.02μB/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 Tc. Polarized neutron scattering reveals that the single resonance is mostly isotropic in spin space, similar to overdoped NaFe0.935Co0.045As but different from optimal electron-, hole-, and isovalently doped BaFe2As2 compounds, all featuring an additional prominent anisotropic component. Spin anisotropy in NaFe0.9785Co0.0215As is instead present at energies below the resonance, which becomes partially gapped below Tc, similar to the situation in optimally doped YBa2Cu3O6.9. Our results indicate that anisotropic spin fluctuations in NaFe1-xCoxAs appear in the form of a resonance in the underdoped regime, become partially gapped below Tc near optimal doping, and disappear in overdoped compounds.",

author = "Yu Song and Weiyi Wang and Chenglin Zhang and Yanhong Gu and Xingye Lu and Guotai Tan and Yixi Su and Fr{\'e}d{\'e}ric Bourdarot and Christianson, {A. D.} and Shiliang Li and Pengcheng Dai",

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T1 - Temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As

AU - Song, Yu

AU - Wang, Weiyi

AU - Zhang, Chenglin

AU - Gu, Yanhong

AU - Lu, Xingye

AU - Tan, Guotai

AU - Su, Yixi

AU - Bourdarot, Frédéric

AU - Christianson, A. D.

AU - Li, Shiliang

AU - Dai, Pengcheng

PY - 2017/11/14

Y1 - 2017/11/14

N2 - We use unpolarized and polarized neutron scattering to study the temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As, with coexisting superconductivity (Tc≈19 K) and weak antiferromagnetic order (TN≈30 K, ordered moment ≈0.02μB/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 Tc. Polarized neutron scattering reveals that the single resonance is mostly isotropic in spin space, similar to overdoped NaFe0.935Co0.045As but different from optimal electron-, hole-, and isovalently doped BaFe2As2 compounds, all featuring an additional prominent anisotropic component. Spin anisotropy in NaFe0.9785Co0.0215As is instead present at energies below the resonance, which becomes partially gapped below Tc, similar to the situation in optimally doped YBa2Cu3O6.9. Our results indicate that anisotropic spin fluctuations in NaFe1-xCoxAs appear in the form of a resonance in the underdoped regime, become partially gapped below Tc near optimal doping, and disappear in overdoped compounds.

AB - We use unpolarized and polarized neutron scattering to study the temperature and polarization dependence of low-energy magnetic fluctuations in nearly optimally doped NaFe0.9785Co0.0215As, with coexisting superconductivity (Tc≈19 K) and weak antiferromagnetic order (TN≈30 K, ordered moment ≈0.02μB/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 Tc. Polarized neutron scattering reveals that the single resonance is mostly isotropic in spin space, similar to overdoped NaFe0.935Co0.045As but different from optimal electron-, hole-, and isovalently doped BaFe2As2 compounds, all featuring an additional prominent anisotropic component. Spin anisotropy in NaFe0.9785Co0.0215As is instead present at energies below the resonance, which becomes partially gapped below Tc, similar to the situation in optimally doped YBa2Cu3O6.9. Our results indicate that anisotropic spin fluctuations in NaFe1-xCoxAs appear in the form of a resonance in the underdoped regime, become partially gapped below Tc near optimal doping, and disappear in overdoped compounds.

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

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