7,530 research outputs found
Synthesizing and characterization of hole doped nickel based layer superconductor (LaSr)ONiAs
We report the synthesizing and characterization of the hole doped Ni-based
superconductor (. By substituting La with Sr, the
superconducting transition temperature is increased from 2.75 K of the
parent phase to 3.7 K at the doping levels x= 0.1 - 0.2. The curve
versus hole concentration shows a symmetric behavior as the electron
doped samples . The normal state resistivity in Ni-based
samples shows a good metallic behavior and reveals the absence of an anomaly
which appears in the Fe-based system at about 150 K, suggesting that this
anomaly is not a common feature for all systems. Hall effect measurements
indicate that the electron conduction in the parent phase is
dominated by electron-like charge carriers, while with more Sr doping, a
hole-like band will emerge and finally prevail over the conduction, and
accordingly the superconducting transition temperature increases.Comment: 4 pages, 5 figure
Temperature dependence and resonance effects in Raman scattering of phonons in NdFeAsOF single crystals
We report plane-polarized Raman scattering spectra of iron oxypnictide
superconductor NdFeAsOF single crystals with varying fluorine
content. The spectra exhibit sharp and symmetrical phonon lines with a weak
dependence on fluorine doping . The temperature dependence does not show any
phonon anomaly at the superconducting transition. The Fe related phonon
intensity shows a strong resonant enhancement below 2 eV. We associate the
resonant enhancement to the presence of an interband transition around 2 eV
observed in optical conductivity. Our results point to a rather weak coupling
between Raman-active phonons and electronic excitations in iron oxypnictides
superconductors.Comment: 4 pages, 3 figures, to appear in Phys. Rev.
Growth and post-annealing studies of La-Bi2201 single crystals
BiSrLaCuO (01.00) single crystals
with high-quality have been grown successfully using the travelling-solvent
floating-zone technique. The patterns of X-ray diffraction suggest high
crystalline quality of the samples. After post-annealing in flowing oxygen at
600 C, the crystals show sharp superconducting transitions revealed by AC
susceptibility. The hole concentration is deduced from superconducting
transition temperature (), which exhibits a linear relation with La doping
level . It ranges from the heavily overdoped regime ( 0.2) to the
extremely underdoped side ( 0.08) where the superconductivity is
absent. Comparing with the superconducting dome in
BiSrCuO system, the effects from out-of-plane
disorders show up in our samples. Besides the La doping level , the
superconductivity is also sensitive to the content of oxygen which could be
tuned by post-annealing method over the whole doping range. The post-annealing
effects on and for each La doping level are studied, which give some
insights on the different nature between overdoped and underdoped regime.Comment: 6 pages, 6 figure
Superconductivity at 36 K in Gadolinium-arsenide Oxides GdOFFeAs
In this paper we report the fabrication and superconducting properties of
GdOFFeAs. It is found that when x is equal to 0.17,
GdOFFeAs is a superconductor with the onset transition
temperature T 36.6K. Resistivity anomaly near 130K was
observed for all samples up to x = 0.17, such a phenomenon is similar to that
of LaOFFeAs. Hall coefficient indicates that
GdOFFeAs is conducted by electron-like charge carriers.Comment: 3 pages, 4 figure
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