Enhancement of the Hall-Lorenz number in optimally doped YBa2Cu3O_7-d

Electronic heat transport in the normal state of a high-quality single crystal of optimally-doped superconductor YBa2Cu3O6.95 was studied by measurements of longitudinal and transverse transport coefficients. For the temperature range from 100 to 300 K, the Hall-Lorenz number (Lxy) depends weakly on temperature and is about two times larger than the Sommerfeld value of the Lorenz number Lo = (pi^2)/3. Our results can be interpreted using a Fermi liquid model when effects of the pseudogap that opens at the Fermi level are included. However, we find that the bipolaron model can also explain both the enhanced value and the weak temperature dependence of the Hall-Lorenz number.Comment: Accepted for publication in Europhysics Letters; 16 pages, 2 figure

Enhancement of the Critical Current Density of YBa2Cu3Ox Superconductors under Hydrostatic Pressure

The dependence of the critical current density Jc on hydrostatic pressure to 0.6 GPa is determined for a single 25-degree [001]-tilt grain boundary in a bicrystalline ring of nearly optimally doped melt-textured YBa2Cu3Ox. Jc is found to increase rapidly under pressure at +20 %/GPa. A new diagnostic method is introduced (pressure-induced Jc relaxation) which reveals a sizeable concentration of vacant oxygen sites in the grain boundary region. Completely filling such sites with oxygen anions should lead to significant enhancements in Jc.Comment: revised manuscript, graphic errors in figures correcte

Student opinions on their development of non-technical skills in IT education

It is recognized that non-technical or soft skills are a vital part of the IT curriculum and hence are considered to be core curriculum components, particularly in the USA and Australia and is also an important worldwide issue. An extensive analysis within an Australian university context found a mismatch between employer expectations and the university-based instruction in these skills. However, it was noted that this unpreparedness in soft skills may be because students may not have appreciated the importance of these skills – a result confirmed by this study, which used a questionnaire delivered to project students undertaking a range of IT based courses. Internships are not common in Australia and hence to address this problem guest speakers from industry are now regularly invited to give presentations to project students. Furthermore it was also found that those students who had workplace experience more fully appreciated the role of workplace soft skills than those who did not have such experience. This study clearly indicates the importance of a team based project unit for teaching soft skills. A further implication is that students need to be made aware of the importance of soft skills in the workplace as a part of their studies

Two-dimensional superconductor-insulator transition in bulk single-crystal YBa_2Cu_3O_(6.38)

We use a magnetic field to tune a highly anisotropic single crystal of oxygen-deficient YBa_2Cu_3O_(7-δ) with a transition temperature of 2 K through the superconductor-insulator transition. The sheet resistance scales with temperature, 0.05≤T≤1.0 K, and field, 0≤H≤94 kOe, in a manner predicted by a theory for quantum phase transitions in disordered two-dimensional superconductors

Influence of oxygen ordering kinetics on Raman and optical response in YBa_2Cu_3O_{6.4}

Kinetics of the optical and Raman response in YBa_2Cu_3O_{6.4} were studied during room temperature annealing following heat treatment. The superconducting T_c, dc resistivity, and low-energy optical conductivity recover slowly, implying a long relaxation time for the carrier density. Short relaxation times are observed for the B_{1g} Raman scattering -- magnetic, continuum, and phonon -- and the charge transfer band. Monte Carlo simulations suggest that these two relaxation rates are related to two length scales corresponding to local oxygen ordering (fast) and long chain and twin formation (slow).Comment: REVTeX, 3 pages + 4 PostScript (compressed) figure