Upper bound on the Andreev states induced second harmonic in the Josephson coupling of YBa2Cu3O7-δ/Nb junctions from experiment and numerical simulations

Theory predicts that d-wave superconductivity induces a significant second harmonic J2 in the Josephson current, as a result of zero-energy Andreev states ZES formed at the junction interface. Consequently, anomalies such as half-integer Shapiro steps and signatures of period doubling of the dc Josephson current versus magnetic field should be observed. We performed experiments on junctions between untwinned d-wave YBa2Cu3O7-δ and Nb and found no trace of such anomalies although clear evidence of Andreev states formation is provided. These findings do not lead to an observable J2. This result combined with extensive numerical simulations put an upper bound on the ZES-induced J2 of about 0.1% from the first harmonic in the Josephson current for tunneling into the 010 direction and of about 2% for tunneling close to the 110 direction. Our results suggest strong J2 suppression by diffusive scattering, which is possibly due to nanoscale interface roughness. This is important for proposed quantum-electronic device concepts based on the expectance of J2

Basic elements for photodeposited high Tc thin film devices

Flat films, high quality insulating layers and adequately superconducting via contacts are basic elements for high Tc device fabrication. We studied the influence of the process parameters of laser deposition on the occurrence of droplets and outgrowths in YBaCuO films. The droplet density is minimal when a laser fluence below about 1.0 J cm-2 is used. The outgrowth density decreases with increasing laser pulse rate or decreasing deposition temperature. High quality flat films were obtained with a rate of 10 Hz and at a temperature of 720 °C. Wet chemical etching and etching with an Argon ion source were used for structuring multilayers with SrTiO3 as an insulating layer. Smooth edges were obtained with an argon gun. Bromine and EDTA etching are not adequate techniques for fabricating controllable well-defined edges. Cross-overs, via contacts and coils were prepared

Conductance anisotropy and linear magnetoresistance in La2-xSrxCuO4 thin films

We have performed a detailed study of conductance anisotropy and magnetoresistance (MR) of La2-xSrxCuO4 (LSCO) thin films (0.10 < x < 0.25). These two observables are promising for the detection of stripes. Subtle features of the conductance anisotropy are revealed by measuring the transverse resistance Rxy in zero magnetic field. It is demonstrated that the sign of Rxy depends on the orientation of the LSCO Hall bar with respect to the terrace structure of the substrate. Unit-cell-high substrate step edges must therefore be a dominant nucleation source for antiphase boundaries during film growth. We show that the measurement of Rxy is sensitive enough to detect the cubic-tetragonal phase transition of the SrTiO3(100) (STO) substrate at 105 K. The MR of LSCO thin films shows for 0.10 < x < 0.25 a non-monotonic temperature dependence, resulting from the onset of a linear term in the MR above 90 K. We show that the linear MR scales with the absolute Hall resistivity, with the constant of proportionality independent of temperature. Such scaling suggests that the linear MR originates from current distortions induced by structural or electronic inhomogeneities. The possible role of stripes for both the MR and the conductance anisotropy is discussed throughout the paper

Novel transport phenomena at complex oxide interfaces

Novel electronic and magnetic phases are being observed at interfaces between insulating, non-magnetic oxide compounds, with the most notable example being the interface between SrTiO3 and LaAlO3. The basic properties of these interfaces will be discussed, as well as prospects for applications and possible future developments

Superconducting Supercomputers and Quantum Computation

Information technologies have been developing at a formidable pace. While miniaturization has been the driver for this in the past decades (Moore\u27s law), the attention is now focusing to the energy consumption. Already a considerable fraction of the worlds\u27 energy use is in information technologies. Also, the on-chip energy dissipation and concomittant high temperatures form a bottleneck in further speeding up processors. For these reasons a great interest exist in the exploration of new computing paradigms. In my presentation, I will introduce two of such paradigms and discuss their current progress and prospects, namely superconducting \u27RSQF\u27 circuitry and quantum-computation. Both technologies require (ultra)-low temperatures, providing interesting challenges for cryogenic engineering

TEM investigation of YBa2Cu3O7 thin films on SrTiO3 bicrystals

YBa2Cu3O7 films in c-axis orientation on bicrystalline SrTiO3 substrates are investigated by TEM. The films and the substrates are examined in cross-section and in plane view. The grain boundary of the bicrystal substrate contains (110) faceted voids, but is otherwise straight on a nanometer scale. Contrary to this, the film grain boundary is not straight grain boundary can be up to 100 nm for a 100 nm thick film. The deviation from the intended position of the YBCO grain boundary can already occur at the film/substrate interface where it can be as much as ±50 nm

How Does Pre-teaching of Vocabulary and the Use of Technology Increase Student Learning in Science

Understanding science vocabulary is one of the key components leading to student success in mastering science content. This study looks at the research surrounding pre-teaching vocabulary and the use of technology in the classroom. The purpose is to further investigate and deepen knowledge of science vocabulary. This research will use mixed methods of data collection. The study reports aggregated data on twenty-seven students of varying academic levels and needs (Regular Education, English Language Learners (ELL), Special Education), within Team 6A, of the 6th grade and data for seven students, who consented for the project, will be evaluated further, through a weekly vocabulary pre- and post-test, content tests, and with the Northwest Evaluation Association (NWEA) Measure of Academic Progress (MAP) Science Growth test to be taken in the fall, winter, and spring. Vocabulary will be presented to students through the use of a Keyword/Information/Memory clue (KIM) chart for pre-teaching, technology programs for investigating meanings and deepening knowledge, and review practice. Advisor: Wendy Smit

Monolithic flux transformer-coupled high-Tc dc SQUID magnetometers

YBa/sub 2/Cu/sub 3/O/sub 7-x/ based monolithic flux transformer-coupled high-T/sub c/ DC SQUID magnetometers operating up to 73 K have been realized. The devices are characterized by high values of the modulation voltage, up to 32 /spl mu/V at 40 K. A minimal white noise level of 0.10 pT//spl radic/Hz was obtained above 200 Hz, and 0.64 pT//spl radic/Hz at 1 Hz and 55 K. The temperature dependence of the modulation voltage, the effective sensing area and the field sensitivity are discussed. Model-calculations have been performed to investigate high frequency resonances in the washer-input coil structure. Methods for damping are considered