Browsing by Author "Huang, Yaobo"

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    Coexistence of Ferromagnetic and Stripe Antiferromagnetic Spin Fluctuations in SrCo2As2
    (American Physical Society, 2019) Li, Yu; Yin, Zhiping; Liu, Zhonghao; Wang, Weiyi; Xu, Zhuang; Song, Yu; Tian, Long; Huang, Yaobo; Shen, Dawei; Abernathy, D.L.; Niedziela, J.L.; Ewings, R.A.; Perring, T.G.; Pajerowski, Daniel M.; Matsuda, Masaaki; Bourges, Philippe; Mechthild, Enderle; Su, Yixi; Dai, Pengcheng
    We use inelastic neutron scattering to study energy and wave vector dependence of spin fluctuations in SrCo2As2, derived from SrFe2−xCoxAs2 iron pnictide superconductors. Our data reveal the coexistence of antiferromagnetic (AF) and ferromagnetic (FM) spin fluctuations at wave vectors QAF=(1,0) and QFM=(0,0)/(2,0), respectively. By comparing neutron scattering results with those of dynamic mean field theory calculation and angle-resolved photoemission spectroscopy experiments, we conclude that both AF and FM spin fluctuations in SrCo2As2 are closely associated with a flatband of the eg orbitals near the Fermi level, different from the t2g orbitals in superconducting SrFe2−xCoxAs2. Therefore, Co substitution in SrFe2−xCoxAs2 induces a t2g to eg orbital switching, and is responsible for FM spin fluctuations detrimental to the singlet pairing superconductivity.
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    Magnetic moment evolution and spin freezing in doped BaFe2As2
    (Springer Nature, 2017) Pelliciari, Jonathan; Huang, Yaobo; Ishii, Kenji; Zhang, Chenglin; Dai, Pengcheng; Chen, Gen Fu; Xing, Lingyi; Wang, Xiancheng; Jin, Changqing; Ding, Hong; Werner, Philipp; Schmitt, Thorsten
    Fe-K β X-ray emission spectroscopy measurements reveal an asymmetric doping dependence of the magnetic moments μbare in electron- and hole-doped BaFe2As2. At low temperature, μbare is nearly constant in hole-doped samples, whereas it decreases upon electron doping. Increasing temperature substantially enhances μbare in the hole-doped region, which is naturally explained by the theoretically predicted crossover into a spin-frozen state. Our measurements demonstrate the importance of Hund’s-coupling and electronic correlations, especially for hole-doped BaFe2As2, and the inadequacy of a fully localized or fully itinerant description of the 122 family of Fe pnictides.