arXiv subjects

Shuai Jiang

Publications and source records attributed to Shuai Jiang.

57 records · Page 4Linked to original sources

arXiv2008

Superconductivity induced by cobalt doping in iron-based oxyarsenides

Chemical doping has recently become a very important strategy to induce superconductivity especially in complex compounds. Distinguished examples include Ba-doped La$_2$CuO$_4$ (the first high temperature superconductor), K-doped BaBiO$_3$, K-doped C$_{60}$ and Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O. The most recent example is F-doped LaFeAsO, which leads to a new class of high temperature superconductors. One notes that all the above dopants are non-magnetic, because magnetic atoms generally break superconducting Cooper pairs. In addition, the doping site was out of the (super)conducting structural unit (layer or framework). Here we report that superconductivity was realized by doping magnetic element cobalt into the (super)conducting-active Fe$_2$As$_2$ layers in LaFe$_{1-x}$Co$_{x}$AsO. At surprisingly small Co-doping level of $x$=0.025, the antiferromagnetic spin-density-wave transition in the parent compound is completely suppressed, and superconductivity with $T_c\sim $ 10 K emerges. With increasing Co content, $T_c$ shows a maximum of 13 K at $x\sim 0.075$, and then drops to below 2 K at $x$=0.15. This result suggests essential differences between previous cuprate superconductor and the present iron-based arsenide one.

cond-mat.supr-con↗

arXiv2008

Thorium-doping induced superconductivity up to 56 K in Gd1-xThxFeAsO

Following the discovery of superconductivity in an iron-based arsenide LaO1-xFxFeAs with a superconducting transition temperature (Tc) of 26 K[1], Tc was pushed up surprisingly to above 40 K by either applying pressure[2] or replacing La with Sm[3], Ce[4], Nd[5] and Pr[6]. The maximum Tc has climbed to 55 K, observed in SmO1-xFxFeAs[7, 8] and SmFeAsO1-x[9]. The value of Tc was found to increase with decreasing lattice parameters in LnFeAsO1-xFx (Ln stands for the lanthanide elements) at an apparently optimal doping level. However, the F- doping in GdFeAsO is particularly difficult[10,11] due to the lattice mismatch between the Gd2O2 layers and Fe2As2 layers. Here we report observation of superconductivity with Tc as high as 56 K by the Th4+ substitution for Gd3+ in GdFeAsO. The incorporation of relatively large Th4+ ions relaxes the lattice mismatch, hence induces the high temperature superconductivity.

cond-mat.supr-con↗

arXiv2005

Enhanced thermopower in an intergrowth cobalt oxide Li$_{0.48}$Na$_{0.35}$CoO$_{2}$

We report the measurements of thermopower, electrical resistivity and thermal conductivity in a complex cobalt oxide Li$_{0.48}$Na$_{0.35}$CoO$_{2}$, whose crystal structure can be viewed as an intergrowth of the O3 phase of Li$_{x}$CoO$_{2}$ and the P2 phase of Na$_{y}$CoO$_{2}$ along the c axis. The compound shows large room-temperature thermopower of $\sim$180 $μ$V/K, which is substantially higher than those of Li$_{x}$CoO$_{2}$ and Na$_{y}$CoO$_{2}$. The figure of merit for the polycrystalline sample increases rapidly with increasing temperature, and it achieves nearly 10$^{-4}$ K$^{-1}$ at 300 K, suggesting that Li$_{x}$Na$_{y}$CoO$_{2}$ system is a promising candidate for thermoelectric applications.

cond-mat.mtrl-sci↗