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Superconducting joints between NbTi and Bi2Sr2Ca2Cu3O10 superconducting wires were successfully fabricated using Bi-added PbSn solders with an in situ sheath-dissolution technique without a removal process for the sheath materials. A backscattered electron image and an energy-dispersive X-ray spectroscopy analysis of the cross-sectional plane of the joints revealed that the joints using Bi-added PbSn solder had a homogeneous morphology with tiny non-superconducting islands. The superconducting joints exhibited high critical currents above 200 A in self-field and 50 A under an applied magnetic field of 5 kOe. [ABSTRACT FROM AUTHOR]

A novel diamond anvil cell specialized for resistivity measurements under high pressure have been developed. Boron-doped metallic diamond electrodes were deposited onto a nano-polycrystalline diamond anvil using a microwave plasma-assisted chemical vapor deposition technique combined with electron beam lithography. The various designs of boron-doped metallic diamond electrodes were demonstrated, and they showed no signs of degradation after repeated compression. [ABSTRACT FROM AUTHOR]

Potassium-intercalated FeSe has been reported as a superconductor with a superconducting transition temperature (Tc) of 30–48 K. However, the relationship among the surface morphology, compositional ratio, and crystal structure has not yet been clarified. This report directly reveals the correspondence among these three characteristics in single crystals with a Tc onset of around 44 K by using a microsampling technique. Island-like parts on the surface of the crystals clearly exhibit the KxFe2Se2 structure with perfect FeSe layers, which is formed in conjunction with the K2Fe4Se5 phase. This results in the appearance of the Tc onset at 44 K. [ABSTRACT FROM AUTHOR]

We have demonstrated a pressure-induced phase transition from a low-Tc phase to a high-Tc phase in a single crystal of the superconductor LaO0.5F0.5BiSe2. The high-Tc phase appears at 2.16 GPa and the maximum superconducting transition temperature is observed at 6.7 K under 2.44 GPa. Although the anisotropy for the low-Tc phase is estimated to be 20, it is reduced by around half (9.3) in the high-Tc phase. This tendency is the same for the BiS2 system. The Tc of LaO0.5F0.5BiSe2 has continued to increase up to the maximum pressure of this study (2.44 GPa). Therefore, applying further pressure has the potential to induce a much higher Tc in this system. [ABSTRACT FROM AUTHOR]

Shubnikov-de Haas oscillations are observed in atomically flat hydrogen-terminated diamond surfaces with high-density hole carriers introduced by the electric field effect using an ionic liquid. The Shubnikov-de Haas oscillations depend only on the magnetic field component perpendicular to the diamond surface, thus providing evidence of two-dimensional Fermi surfaces. The effective masses estimated from the temperature dependence of the oscillations are close to the cyclotron effective masses of the valence band maxima in diamond. The estimated quantum scattering time is one order of magnitude longer than the transport scattering time and indicates that the carrier mobility is locally as high as several thousand cm2/V s at low temperature. [ABSTRACT FROM AUTHOR]

We prepared single crystalline SmFeAsO1-xFx with an exceptionally high fluorine concentration by using a CsCl flux method. Comparing to conventional flux methods, this method can introduce about double the amount of fluorine into the oxygen site. The obtained single crystal shows the highest superconducting transition temperature (Tc = 57.5 K) in single crystalline iron pnictides. In addition, the residual resistivity ratio is almost three times as large as that of previously reported single crystals. This suggests that our single crystals are suitable for investigation of the intrinsic superconducting properties, since they have few defects and impurities. Using both the Werthamer-Helfand-Hohenberg model and the effective mass model, we demonstrated that a higher fluorine concentration suppresses the anisotropic superconductivity of SmFeAsO1-xFx [ABSTRACT FROM AUTHOR]

The effects of uniaxial strain and hydrostatic pressure on Hg0.83Re0.18Ba2Ca2.4Cu3.6O14[Hg0.83(Re0.18)-1223] were investigated by ac magnetic measurements under stress corresponding to a pressure of 20 GPa at maximum. According to a previous thermal study based on the Ehrenfest relation, in-plane contraction should increase the superconducting transition temperature Tc, whereas out-of-plane contraction should decrease Tc. This suggests that the increase in Tc under hydrostatic-pressure contraction must be smaller than that under in-plane contraction. However, the present uniaxial-strain experiments revealed enhancement of Tc under both in-plane and out-of-plane contraction, and the largest enhancement was observed under hydrostatic-pressure contraction. According to a band calculation, all contraction styles induce hole doping from the HgO blocks to the CuO2 blocks, and hydrostatic-pressure contraction yields the largest hole doping among three contractions. This behavior explains well a series of changes in Tc in the stress region of below 8 GPa. More specifically, under hydrostatic-pressure contraction, Tc exhibited an increase, a decrease, and another increase with increasing pressure, and this multistep change is similar to that observed in Bi-2223-type cuprate superconductors, suggesting that it is necessary to distinguish the effect of strain on the middle CuO2 plane in the three-CuO2-plane package from that on the outer planes. [ABSTRACT FROM AUTHOR]

We report magnetoresistance measurements of hydrogen-terminated (100)-oriented diamond surfaces wherein an ionic-liquid-gated field-effect-transistor technique was used to make hole carriers accumulate. Unexpectedly, the observed magnetoresistance is positive within the range of 2