In-gap features in superconducting LaAlO3_3-SrTiO3_3 interfaces observed by tunneling spectroscopy

We identified quasiparticle states at well-defined energies inside the superconducting gap of the electron system at the LaAlO$_3$-SrTiO$_3$ interface using tunneling spectroscopy. The states are found only in a number of samples and depend upon the thermal-cycling history of the samples. The states consist of a peak at zero energy and other peaks at finite energies, symmetrically placed around zero energy. These peaks disappear, together with the superconducting gap, with increasing temperature and magnetic field. We discuss the likelihood of various physical mechanisms that are known to cause in-gap states in superconductors and conclude that none of these mechanisms can easily explain the results. The conceivable scenarios are the formation of Majorana bound states, Andreev bound states, or the presence of an odd-frequency spin triplet component in the superconducting order parameter.Comment: 11 pages, 5 figure

Screened-interaction expansion for the Hubbard model and determination of the quantum Monte Carlo Fermi surface

We develop a systematic self-consistent perturbative expansion for the self energy of Hubbard-like models. The interaction lines in the Feynman diagrams are dynamically screened by the charge fluctuations in the system. Although the formal expansion is exact-assuming that the model under the study is perturbative-only if diagrams to all orders are included, it is shown that for large-on-site-Coulomb-repulsion-U systems weak-coupling expansions to a few orders may already converge. We show that the screened interaction for the large-U system can be vanishingly small at a certain intermediate electron filling; and it is found that our approximation for the imaginary part of the one-particle self energy agrees well with the QMC results in the low energy scales at this particular filling. But, the usefulness of the approximation is hindered by the fact that it has the incorrect filling dependence when the filling deviates from this value. We also calculate the exact QMC Fermi surfaces for the two-dimensional (2-D) Hubbard model for several fillings. Our results near half filling show extreme violation of the concepts of the band theory; in fact, instead of growing, Fermi surface vanishes when doped toward the half-filled Mott-Hubbard insulator. Sufficiently away from half filling, noninteracting-like Fermi surfaces are recovered. These results combined with the Luttinger theorem might show that diagrammatic expansions for the nearly-half-filled Hubbard model are unlikely to be possible; however, the nonperturbative part of the solution seems to be less important as the filling gradually moves away from one half. Results for the 2-D one-band Hubbard model for several hole dopings are presented. Implications of this study for the high-temperature superconductors are also discussed.Comment: 11 pages, 12 eps figures embedded, REVTeX, submitted to Phys. Rev. B; (v2) minor revisions, scheduled for publication on November 1

NEAR: New Earths in the Alpha Cen Region (bringing VISIR as a "visiting instrument" to ESO-VLT-UT4)

By adding a dedicated coronagraph, ESO in collaboration with the Breakthrough Initiatives, modifies the Very Large Telescope mid-IR imager (VISIR) to further boost the high dynamic range imaging capability this instru- ment has. After the VISIR upgrade in 2012, where coronagraphic masks were first added to VISIR, it became evident that coronagraphy at a ground-based 8m-class telescope critically needs adaptive optics, even at wavelengths as long as 10μm. For VISIR, a work-horse observatory facility instrument in normal operations, this is ”easiest” achieved by bringing VISIR as a visiting instrument to the ESO-VLT-UT4 having an adaptive M2. This “visit” enables a meaningful search for Earth-like planets in the habitable zone around both α-Cen1,2. Meaningful here means, achieving a contrast of ≈ 10^(-6) within ≈ 0.8arcsec from the star while maintaining basically the normal sensitivity of VISIR. This should allow to detect a planet twice the diameter of Earth. Key components will be a diffractive coronagraphic mask, the annular groove phase mask (AGPM), optimized for the most sensitive spectral band-pass in the N-band, complemented by a sophisticated apodizer at the level of the Lyot stop. For VISIR noise filtering based on fast chopping is required. A novel internal chopper system will be integrated into the cryostat. This chopper is based on the standard technique from early radio astronomy, conceived by the microwave pioneer Robert Dicke in 1946, which was instrumental for the discovery of the 3K radio background

Measurement of the very rare K+→π+ννˉK^+ \to \pi^+ \nu \bar\nu decay

The decay K+→π+νν¯ , with a very precisely predicted branching ratio of less than 10−10 , is among the best processes to reveal indirect effects of new physics. The NA62 experiment at CERN SPS is designed to study the K+→π+νν¯ decay and to measure its branching ratio using a decay-in-flight technique. NA62 took data in 2016, 2017 and 2018, reaching the sensitivity of the Standard Model for the K+→π+νν¯ decay by the analysis of the 2016 and 2017 data, and providing the most precise measurement of the branching ratio to date by the analysis of the 2018 data. This measurement is also used to set limits on BR(K+→π+X ), where X is a scalar or pseudo-scalar particle. The final result of the BR(K+→π+νν¯ ) measurement and its interpretation in terms of the K+→π+X decay from the analysis of the full 2016-2018 data set is presented, and future plans and prospects are reviewed

Is de rode Amerikaanse rivierkreeft een ernstige bedreiging voor het veenweidegebied?

Sinds 2010 worden in het veenweidegebied van Zuid Holland en Utrecht zeer hoge dichtheden van de rode Amerikaanse rivierkreeft (Procambarus clarckii) aangetroffen. Deze exoot uit Mexico en het zuiden van de Verenigde Staten werd in 1973 uitgezet in Spanje, vooral om de lokale visserij te stimuleren. Van hier uit heeft deze soort zich snel over Europa verspreid. In dit artikel wordt aan de hand van gegevens over juffers en libellen in de Molenpolder bij Utrecht ingegaan op de effecten en mogelijke aanpak van deze soort

Arthur Kampf

ARTHUR KAMPF Arthur Kampf ([1]r) Cover ( - ) Title page ([1]r) Preface ([1]v) Inhalt ([2]v) 1. Richard II. ([1]r) 2. Heinrich IV. ([2]r) 3. Heinrich VI. ([3]r) 4. Richard III. ([4]r) 5. Heinrich VIII. ([5]r) 6. Julius Caesar ([6]r) 7. Die beiden Veroneser ([7]r) 8. Sommernachtstraum ([8]r) 9. Der Widerspenstigen Zähmung ([9]r) 10. Der Kaufmann von Venedig ([10]r) 11. Die Lustigen Weiber von Windsor ([11]r) 12. Was Ihr Wollt ([12]r) 13. Hamlet ([13]r) 14. Othello ([14]r) 15. König Lear ([15]r) 16. Troilus und Cresside ([16]r) 17. Wintermärchen ([17]r) 18. Der Sturm ([18]r) 19. Venus und Adonis ([19]r) 20. Schändung der Lucrezia ([20]r

Is de rode Amerikaanse rivierkreeft een ernstige bedreiging voor het veenweidegebied?

Sinds 2010 worden in het veenweidegebied van Zuid Holland en Utrecht zeer hoge dichtheden van de rode Amerikaanse rivierkreeft (Procambarus clarckii) aangetroffen. Deze exoot uit Mexico en het zuiden van de Verenigde Staten werd in 1973 uitgezet in Spanje, vooral om de lokale visserij te stimuleren. Van hier uit heeft deze soort zich snel over Europa verspreid. In dit artikel wordt aan de hand van gegevens over juffers en libellen in de Molenpolder bij Utrecht ingegaan op de effecten en mogelijke aanpak van deze soort