Zhu-An Xu

Fermi surface nesting induced strong pairing in iron-based superconductors.

The discovery of high-temperature superconductivity in iron pnictides raised the possibility of an unconventional superconducting mechanism in multiband materials. The observation of Fermi-surface (FS)-dependent nodeless superconducting gaps suggested that inter-FS interactions may play a crucial role in superconducting pairing. In the optimally hole-doped Ba0.6K0.4Fe2As2, the pairing strength is enhanced simultaneously (2Δ/Tc≈7) on the nearly nested FS pockets, i.e., the inner hole-like (α) FS and the 2 hybridized electron-like FSs, whereas the pairing remains weak (2Δ/Tc≈3.6) in the poorly nested outer hole-like (β) FS. Here, we report that in the electron-doped BaFe1.85Co0.15As2, the FS nesting condition switches from the α to the β FS due to the opposite size changes for hole- and electron-like FSs upon electron doping. The strong pairing strength (2Δ/Tc≈6) is also found to switch to the nested β FS, indicating an intimate connection between FS nesting and superconducting pairing, and strongly supporting the inter-FS pairing mechanism in the iron-based superconductors.

On the origin of ferromagnetism in CeO2 nanocubes

Magnetic behaviors of pure CeO2 nanoparticles and nanocubes have been investigated both experimentally and theoretically. It is found that monodisperse CeO2 nanocubes with an average size of 5.3 nm do show ferromagnetic behavior at ambient temperature with a saturation magnetization of about 5.7 memu/g and coercive force of about 69 Oe. First-principles calculations reveal that oxygen vacancies in pure CeO2 cause spin polarization of f electrons for Ce ions surrounding oxygen vacancies, resulting in net magnetic moment for pure CeO2 samples. One oxygen vacancy at surface can induce more magnetic moments than those induced by one oxygen vacancy in bulk. The results obtained here provide evidence that pure CeO2 sample with oxygen vacancies can indeed have magnetic behavior. This study will stimulate more investigations for understanding the origin of ferromagnetic TM-doped CeO2 (TM=3d transition metals) in a particular case and TM-doped semiconductor oxides in general at ambient temperature.

Superconductivity induced by La doping in Sr1−xLaxFBiS2

Through a combination of x-ray diffraction, electrical transport, magnetic susceptibility, and heat-capacity measurements, we report the effect of La doping on Sr in the newly discovered SrFBiS

Effects of cobalt doping and phase diagrams of LFe1-xCox AsO (L=La and Sm)

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Superconductivity in LaFeAs1-xPxO: effect of chemical pressures and bond covalency

system. Superconducting transition with critical temperature T

Helicity protected ultrahigh mobility Weyl fermions in NbP

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Possible charge-density wave, superconductivity, andf-electron valence instability inEuBiS2F

of 2.8 K, developed from a semiconducting-like normal state, was found in Sr

Ba2Ti2Fe2As4O: A New Superconductor Containing Fe2As2 Layers and Ti2O Sheets

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Optical investigations of the normal and superconducting states reveal two electronic subsystems in iron pnictides

La

Unconventional superconductivity in quasi-one-dimensionalRb2Cr3As3

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