Induced Superconductivity in Hybrid Au/YBa2Cu3O7-x Electrodes on Vicinal Substrates

Superconducting electrodes are an integral part of hybrid Josephson junctions used in many applications including quantum technologies. We report on the fabrication and characterization of superconducting hybrid Au/YBa2Cu3O7-x (YBCO) electrodes on vicinal substrates. In these structures, superconducting CuO2-planes face the gold film, resulting in a higher value and smaller variation of the induced energy gap compared to the conventional Au/YBCO electrodes based on films with the c-axis normal to the substrate surface. Using scanning tunneling microscopy, we observe an energy gap of about 10-17 meV at the surface of the 15- nm-thick gold layer deposited in situ atop the YBCO film. To study the origin of this gap, we fabricate nanoconstrictions from the Au/YBCO heterostructure and measure their electrical transport characteristics. The conductance of the nanoconstrictions shows a series of dips due to multiple Andreev reflections in YBCO and gold providing clear evidence of the superconducting nature of the gap in gold. We consider the Au/YBCO electrodes to be a versatile platform for hybrid Josephson devices with a high operating temperature

Empirische Shortcuts:Studentische Forschungsprojekte in der Methodenlehre

Die empirische Bildungsforschung hat in den letzten Jahren einen nachhaltigen quantitativen und qualitativen Aufschwung genommen. Erziehungswissenschaftliche Forschung erschöpft sich jedoch nicht im M&E des schulischen Lernstands im nationalen und internationalen Vergleich und seiner Ursachen sondern umfasst ein weites Feld an Fragestellungen aus unterschiedlichsten Bereichen. Dies muss den Studierenden, neben den methodischen Modellen und Instrumentarien exemplarisch vermittelt werden. Das ideale didaktische Modell hierfür ist zweifellos ein von den Studierenden selbst konzipiertes und durchgeführtes Forschungsprojekt, wie es seit Jahren im Programmbereich „Empirische Pädagogik“ des Instituts für Erziehungswissenschaft der WWU Münster praktiziert. Dadurch werden den Studierenden Dimensionen eröffnet, die im Zeitalter von Modularisierung, OECD-Statistiken und Ressourcenverknappung sich zunehmend verengen. Die damit verbundenen Impulse und Erfahrungsgewinne sind in eine Belebung und Bereicherung des Studiums

PAPER-64 Constraints On Reionization II: The Temperature Of The z=8.4 Intergalactic Medium

We present constraints on both the kinetic temperature of the intergalactic medium (IGM) at z=8.4, and on models for heating the IGM at high-redshift with X-ray emission from the first collapsed objects. These constraints are derived using a semi-analytic method to explore the new measurements of the 21 cm power spectrum from the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER), which were presented in a companion paper, Ali et al. (2015). Twenty-one cm power spectra with amplitudes of hundreds of mK^2 can be generically produced if the kinetic temperature of the IGM is significantly below the temperature of the Cosmic Microwave Background (CMB); as such, the new results from PAPER place lower limits on the IGM temperature at z=8.4. Allowing for the unknown ionization state of the IGM, our measurements find the IGM temperature to be above ~5 K for neutral fractions between 10% and 85%, above ~7 K for neutral fractions between 15% and 80%, or above ~10 K for neutral fractions between 30% and 70%. We also calculate the heating of the IGM that would be provided by the observed high redshift galaxy population, and find that for most models, these galaxies are sufficient to bring the IGM temperature above our lower limits. However, there are significant ranges of parameter space that could produce a signal ruled out by the PAPER measurements; models with a steep drop-off in the star formation rate density at high redshifts or with relatively low values for the X-ray to star formation rate efficiency of high redshift galaxies are generally disfavored. The PAPER measurements are consistent with (but do not constrain) a hydrogen spin temperature above the CMB temperature, a situation which we find to be generally predicted if galaxies fainter than the current detection limits of optical/NIR surveys are included in calculations of X-ray heating.Comment: companion paper to Ali et al. (2015), ApJ 809, 61; matches version accepted to ApJ; 11 pages, 7 figure