Tunneling magnetoresistance studies of Sr3 Ru2 O7

We have performed planar tunneling measurements on Sr3Ru2O7, which has a field-tuned metamagnetic quantum phase transition. Our previously reported work revealed an unusual oscillation in the tunneling magnetoresistance of junctions made on Sr3Ru2O7 single crystals J. Hooper et al., Phys. Rev. Lett. 92, 257206 �2004�. We here report further characterization of this intriguing phenomenon, revealing that the oscillation has a systematic dependence on the tunnel barrier, field orientation, and temperature. We discuss possible origins of this unusual oscillation phenomenon in light of these new experimental results

Critical current of the Sr2RuO4-Sr3Ru2O7 eutectic system

We report critical current measurements of the Sr2RuO4-Sr3Ru2O7 eutectic system, a solid mixture of the spin-triplet superconductor Sr2RuO4 and the nearly ferromagnetic metal Sr3Ru2O7. Our results reveal that this eutectic forms an unusual superconducting state with features distinct from those of the pure Sr2RuO4 phase. We observe a crossover from Ambegaokar-Baratoff to Ginzburg-Landau type behavior in the temperature dependence of the critical current, similar to the behavior of Josephson weak-link networks in granular highTc cuprates. Our results suggest that large regions of Sr3Ru2O7 in this solid mixture may become superconducting by an unusual proximity effect

Superconductivity close to magnetic instability in Fe(Se 1-xTex)0.82

We report our study of the evolution of superconductivity and the phase diagram of the ternary Fe(Se1-xTex)0.82 (0≤x≤1.0) system. We discovered a superconducting phase with T c,max=14 K in the 0.3<x<1.0 range. This superconducting phase is suppressed when the sample composition approaches the end member FeTe 0.82, which exhibits an incommensurate antiferromagnetic order. We discuss the relationship between the superconductivity and magnetism of this material system in terms of recent results from neutron-scattering measurements. Our results and analyses suggest that superconductivity in this class of Fe-based compounds is associated with magnetic fluctuations and therefore may be unconventional in nature

Probing electrode/electrolyte interfacial structure in the potential region of hydrogen evolution by Raman spectroscopy

The detailed interfacial structure in the potential region of severe hydrogen evolution, to date, is far from clear due to lack of both experimental data and correlated theoretic models. It has been shown that it is possible to surmount, to some extent, the disturbance of the spectroelectrochemical measurement by strong hydrogen bubbling in the potential region of severe hydrogen evolution by using a surface enhancement effect and a thin-layer cell configuration. Using this approach, we have obtained surface enhanced Raman scattering (SERS) spectra of water at an Ag electrode at very negative potentials at various concentrations of NaClO4. To explain the abnormal reversal of the peak intensity ratio of the bending to the stretching vibration, a preliminary model of the electrode/electrolyte interface is presented. The water molecule is oriented with one hydrogen attached to the surface and the oxygen towards an adsorbed cation which is partially dehydrated owing to the very strong electrostatic force. Raman spectra of hydrogen bound at a Pt electrode in solutions of varying pH from 0 to 14 at potentials of mild hydrogen evolution have also been presented for the first time. The spectra reveal that the Pt-hydrogen interaction is influenced by both the potential and the interfacial structure. These primary studies may initiate more molecular-level research of electrochemical interfaces in the potential region of hydrogen evolution

Surface enhanced Raman scattering from bare cobalt electrode surfaces

Surface enhanced Raman spectra (SERS) of adsorbed species from a bare cobalt (Co) bulk electrode were observed for the first time with confocal Raman microscopy. A combined AFM, Raman and electrochemical study shows that a proper roughening procedure is vitally important for obtaining good-quality surface Raman spectra from the Co electrode. The surface enhancement factor ranges from 2 to 3 orders of magnitude, depending critically on the surface roughening procedure. The present study provides a bright prospect for the wide investigation of systems of practical application

Dislocations and the enhancement of superconductivity in odd-parity superconductor Sr2_2RuO4_4

We report observation of the enhancement of superconductivity near lattice dislocations and the absence of the strengthening of vortex pinning in odd-parity superconductor Sr$_2$RuO$_4$, both surprising results in direct contrast to the well known sensitivity of superconductivity in Sr$_2$RuO$_4$ to disorder. The enhanced superconductivity appears to be related fundamentally to the two-component nature of the superconducting order parameter, as revealed in our phenomenological theory taking into account the effect of symmetry reduction near a dislocation.Comment: 5 pages, 4 figures, submitted to Physical Review Letter

Overexpression of a Common Wheat Gene TaSnRK2.8 Enhances Tolerance to Drought, Salt and Low Temperature in Arabidopsis

Drought, salinity and low temperatures are major factors limiting crop productivity and quality. Sucrose non-fermenting1-related protein kinase 2 (SnRK2) plays a key role in abiotic stress signaling in plants. In this study, TaSnRK2.8, a SnRK2 member in wheat, was cloned and its functions under multi-stress conditions were characterized. Subcellular localization showed the presence of TaSnRK2.8 in the cell membrane, cytoplasm and nucleus. Expression pattern analyses in wheat revealed that TaSnRK2.8 was involved in response to PEG, NaCl and cold stresses, and possibly participates in ABA-dependent signal transduction pathways. To investigate its role under various environmental stresses, TaSnRK2.8 was transferred to Arabidopsis under control of the CaMV-35S promoter. Overexpression of TaSnRK2.8 resulted in enhanced tolerance to drought, salt and cold stresses, further confirmed by longer primary roots and various physiological characteristics, including higher relative water content, strengthened cell membrane stability, significantly lower osmotic potential, more chlorophyll content, and enhanced PSII activity. Meanwhile, TaSnRK2.8 plants had significantly lower total soluble sugar levels under normal growing conditions, suggesting that TaSnRK2.8 might be involved in carbohydrate metabolism. Moreover, the transcript levels of ABA biosynthesis (ABA1, ABA2), ABA signaling (ABI3, ABI4, ABI5), stress-responsive genes, including two ABA-dependent genes (RD20A, RD29B) and three ABA-independent genes (CBF1, CBF2, CBF3), were generally higher in TaSnRK2.8 plants than in WT/GFP controls under normal/stress conditions. Our results suggest that TaSnRK2.8 may act as a regulatory factor involved in a multiple stress response pathways