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Spin excitations in electron-doped iron superconductors Pengcheng Dai, University of Tennessee Knoxville, DMR 1063866.

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  1. Spin excitations in electron-doped iron superconductorsPengcheng Dai, University of Tennessee Knoxville, DMR 1063866 Since the discovery of the metallic antiferromagnetic (AF) ground state near superconductivity in iron pnictide superconductors, a central question has been whether magnetism in these materials arises from weakly correlated electrons, as in the case of spin density wave in pure chromium, requires strong electron correlations, or can even be described in terms of localized electrons such as the AF insulating state of copper oxides. Here we use inelastic neutron scattering to determine the absolute intensity of the magnetic excitations throughout the Brillouin zone in electron-doped superconducting BaFe1.9Ni0.1As2 (Tc =20 K), which allows us to obtain the size of the fluctuating magnetic momentand its energy distribution. We find that superconducting sample and AF BaFe2As2 both have fluctuating magnetic moments similar to those found in the AF insulating copper oxides. The common theme in both classes of high-temperature superconductors is that magnetic excitations have partly localized character, thus showing the importance of strong correlations for high-temperature superconductivity (Nature Physics 8, 376 (2012)).

  2. Spin excitations in electron-doped iron superconductors Pengcheng Dai, University of Tennessee Knoxville, DMR 1063866 There are a total of 3 graduate students and 2 undergraduate student supported in part by the present NSF, including Leland Harriger, Miaoyin Wang, Mengshu Liu, and undergraduate student Tucker Netherton and Zachary Sims. The participation of graduate/undergraduate students in our program has greatly enhanced interactions amongst students, and promoted neutron science in general. Both graduate and undergraduate students have played important role in our NSF supported neutron scattering work on understanding the role of magnetism in the high-temperature superconductivity of iron pnictides. Publications resulted from the NSF support: PRB 84, 054544 (2011); Nature Communications 2, 580 (2011); PRB 85, 054511 (2012)), PRL 108, 247002 (2012); PRB 85, 214516 (2012); Nature Physics 8, 376 (2012).

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