Universal linear-temperature dependence of static magnetic susceptibility in iron-pnictides

A universal linear-temperature dependence of the uniform magnetic susceptibility has been observed in the nonmagnetic normal state of iron-pnictides. This non-Pauli and non-Curie-Weiss-like paramagnetic behavior cannot be understood within a pure itinerant picture. We argue that it results from the existence of a wide antiferromagnetic fluctuation window in which the local spin-density-wave correlations exist but the global directional order has not been established yet.Comment: 4 pages, 2 figure

Elastic theory for the vortex-lattice melting in iron-based high-Tc superconductors

The vortex-lattice melting transitions in two typical iron-based high-Tc superconductor $Ba(Fe_{1-x}Co_{x})_{2}As_{2}$ (122-type) and$Nd(O_{1-x}F_{x})FeAs$ (1111-type) for magnetic fields both parallel and perpendicular to the anisotropy axis are studied within the elastic theory. Using the parameters from experiments, the vortex-lattice melting lines in the H-T diagram are located systematically by various groups of Lindemann numbers. It is observed that the theoretical result for the vortex melting on $Ba(Fe_{1-x}Co_{x})_{2}As_{2}$ for parallel fields agrees well the recent experimental data. The future experimental results for the vortex melting can be compared with the present theoretical prediction by tuning reasonable Lindemann numbers.Comment: 10 pages, 5 figure

Near-degeneracy of several pairing channels in multiorbital models for the Fe-pnictides

Weak-coupling approaches to the pairing problem in the iron pnictide superconductors have predicted a wide variety of superconducting ground states. We argue here that this is due both to the inadequacy of certain approximations to the effective low-energy band structure, and to the natural near-degeneracy of different pairing channels in superconductors with many distinct Fermi surface sheets. In particular, we review attempts to construct two-orbital effective band models, the argument for their fundamental inconsistency with the symmetry of these materials, and the comparison of the dynamical susceptibilities in two- and five-orbital models. We then present results for the magnetic properties, pairing interactions, and pairing instabilities within a five-orbital Random Phase Approximation model. We discuss the robustness of these results for different dopings, interaction strengths, and variations in band structure. Within the parameter space explored, an anisotropic, sign-changing s-wave state and a d_x2-y2 state are nearly degenerate, due to the near nesting of Fermi surface sheets.Comment: 17 pages, 23 figure

Universal linear-temperature dependence of static magnetic susceptibility in iron pnictides

A universal linear-temperature dependence of the uniform magnetic susceptibility has been observed in the non-magnetic normal state of iron pnictides. This non-Pauli and non-Curie-Weiss-like paramagnetic behavior cannot be understood within a simple mean-field picture. We argue that it results from the existence of a wide antiferromagnetic fluctuation window in which the local spin-density-wave correlations exist but the global directional order has not been established yet

Chemistry and biochemistry of Terpenoids from Curcumaand related species

Several curcuminoids have been identified from rhizome of the common spice Curcuma longa (Zingaberaceae) and related plant species. Curcuminoids are known to display several pharmacological properties summed up in numerous papers and reviews. In addition to curcuminoids, more than 250 mono-, sesqui- di-, and triterpenoids have been identified from curcuma species. These lipophilic compounds have better absorption than curcuminoids and also exhibit a wide spectrum of pharmacological properties. Little attention has been paid to these lipophilic compounds, which may be as physiologically active, if not more, as curcuminoids. This review focuses on Curcuma terpenoids and their physiological properties