Robust Upward Dispersion of the Neutron Spin Resonance in the Heavy Fermion Superconductor Ce1−x_{1-x}Ybx_{x}CoIn5_5

The neutron spin resonance is a collective magnetic excitation that appears in copper oxide, iron pnictide, and heavy fermion unconventional superconductors. Although the resonance is commonly associated with a spin-exciton due to the $d$($s^{\pm}$)-wave symmetry of the superconducting order parameter, it has also been proposed to be a magnon-like excitation appearing in the superconducting state. Here we use inelastic neutron scattering to demonstrate that the resonance in the heavy fermion superconductor Ce$_{1-x}$Yb$_{x}$CoIn$_5$ with $x=0,0.05,0.3$ has a ring-like upward dispersion that is robust against Yb-doping. By comparing our experimental data with random phase approximation calculation using the electronic structure and the momentum dependence of the $d_{x^2-y^2}$-wave superconducting gap determined from scanning tunneling microscopy for CeCoIn$_5$, we conclude the robust upward dispersing resonance mode in Ce$_{1-x}$Yb$_{x}$CoIn$_5$ is inconsistent with the downward dispersion predicted within the spin-exciton scenario.Comment: Supplementary Information available upon reques

Superconducting and normal state properties of the systems La1−xMxPt4Ge12 (M=Ce,Th)

Electrical resistivity, magnetization, and specific heat measurements were performed on polycrystalline samples of the filled-skutterudite systems La1−xMxPt4Ge12 (M = Ce and Th). Superconductivity in LaPt4Ge12 was quickly suppressed with Ce substitution and no evidence for superconductivity was found down to 1.1 K for x \u3e 0.2. Temperature-dependent specific heat data at low temperatures for La1−xCexPt4Ge12 show a change from powerlaw to exponential behavior, which may be an indication for multiband superconductivity in LaPt4Ge12. A similar crossover was observed in the Pr1−xCexPt4Ge12 system. However, the suppression rates of the superconducting transition temperatures Tc(x) in the two systems are quite disparate, indicating a difference in the nature of superconductivity, which is conventional in LaPt4Ge12 and unconventional in PrPt4Ge12. In comparison, a nearly linear and smooth evolution of Tc with increasing Th was observed in the La1−xThxPt4Ge12 system, with no change of the superconducting energy gap in the temperature dependence of the specific heat, suggesting similar types of superconductivity in both the LaPt4Ge12 and ThPt4Ge12 compounds

Neuro-Behçet: a clinical exercise

Behçet disease is a recurrent systemic vasculitis of unknown etiology, that involves vessels of nearly all sizes and types. Because of this, disease manifestations can occur at many sites throughout the body. Central nervous system (CNS) involvement may be parenchymal or nonparenchymal and has a global prevalence that ranges from 3% to 10%. Main signs of CNS involvement are pyramidal and those resulting from brain stem lesions. Aseptic meningitis, mental changes, sphincter disturbances, pseudobulbar syndrome, and deep sensory abnormalities may be seen. Analysis of cerebrospinal fluid, computed tomography (CT), magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT) and brain angiography offer assistance in the diagnosis. The course of disease can be primary progressive, secondary progressive or have a relapsing-remitting profile. Boluses of methylprednisolone for three days followed by cyclophosphamide are the treatment of choice. This papers discusses these aspects of neuro-Behcet on the basis of complex clinical cas