Bulk superconductivity in Bi4O4S3 revealed by specific heat measurement

Specific heat experiments on a well-characterized polycrystalline sample of the BiS2 based superconductor Bi4O4S3 revealed that it shows a crear specific heat anomaly at about Tc = 4.4 K, consistent with Tc from the resistivity and dc susceptibility. This observation indicates the superconductivity of Bi4O4S3 to be bulk in nature

Superconductivity in S-substituted FeTe

We have successfully synthesized a new superconducting phase of FeTe1-xSx with a PbO-type structure. It has the simplest crystal structure in iron-based superconductors. Superconducting transition temperature is about 10 K at x = 0.2. The upper critical field Hc2 was estimated to be ~70 T. The coherent length was calculated to be ~2.2 nm. Because FeTe1-xSx is composed of nontoxic elements, this material is a candidate for applications and will activate more and more research on iron-based superconductor.Comment: 13 pages, 10 figure

Alcoholic beverages induce superconductivity in FeTe1−x_{1-x}Sx_x

We found that hot alcoholic beverages were effective in inducing superconductivity in FeTe$_{0.8}$S0$_{.2}$. Heating FeTe$_{0.8}$S0$_{.2}$ compound in various alcoholic beverages enhances the superconducting properties compared to pure water-ethanol mixture as a control. Heating with red wine for 24 hours leads to the largest shielding volume fraction of 62.4% and the highest zero resistivity temperature of 7.8 K. Some components present in alcoholic beverages, other than water and ethanol, have the ability to induce superconductivity in FeTe$_{0.8}$S0$_{.2}$ compound.Comment: 12 pages, 4 figures, accepted for publication in Supercond. Sci. Techno

Pressure study of the new iron-based superconductor K0.8Fe2Se2

We investigated pressure effects on transition temperature (Tc) of the new iron-based superconductor K0.8Fe2Se2 using a BeCu/NiCrAl hybrid-type clamped piston-cylinder cell. The Tc(onset) was 33K at 0.85 GPa. With increasing pressure, Tc(onset) gradually increased and reached 36.6 K at 2.03 GPa.Comment: 8 pages, 3 figure

Nonlinear Dynamics of Collapse Phenomena in Heliotron Plasma with Large Pressure Gradient

We have executed nonlinear magnetohydrodynamic(MHD) simulations in a heliotron-type configuration with a large pressure gradient to reveal the nonlinear dynamics of collapse phenomena. The simulation results reproduce the qualitative characteristics of the experimental observation on the so-called core density collapse (CDC) events in the Large Helical Device (LHD) plasma with the super dense core (SDC) profile. A long-term nonlinear behavior on the event, including the flushing mechanism of the core pressure, is clarified. The simulation result shows the linear growth of the ballooning-like resistive instability modes with the intermediate poloidal wavenumbers. The growth of the modes are saturated soon, and the system experiences the energy relaxation in about 1 msec. It should be noted that the linear mode structures are localized in the edge region, whereas the core pressure rapidly falls as the system reaches the relaxed state. The co-existence of the edge perturbation and the core collapse is consistent with the experimental observations. The lost pressure forms a wider tail in the peripheral region. The core pressure is remarkably reduced at a certain period, while it had withstood the disturbance before it. The most salient feature on this period is the disordering of the magnetic field structure. The system keeps the nested-flux-surface structure well in the beginnings, whereas part of them are abruptly lost at this period. Such a situation can induce a flattening of the pressure profile along the reconnected field lines. By checking the place where the plasma loss due to this mechanism occurs, such plasma outlets are found to be located mainly on the disordered region. Thus, one can conclude that the core collapse can be caused by the disturbance of the magnetic field