1,721,002 research outputs found
A tunneling spectroscopy study of the pairing symmetry in the electron-doped Pr1−xLaCexCuO4−y
No full textWe have performed scanning tunneling spectroscopy and point contact spectroscopy
measurements on the electron-doped superconductor Pr1−xLaCexCuO4−y (x = 0.12,
Tc ? 25 K). We address the question of the symmetry of the order parameter and of the
amplitude of the energy gap. We compare three possible scenarios, i.e. isotropic s-wave,‘anisotropic’ s-wave, and d-wave. Evidence for a d-wave symmetry of the order parameter is given. From the temperature evolution of the dI/dV versus V characteristics we extract a
BCS-like temperature dependence of the superconducting energy gap ?. Despite the variety of measured spectra we give a consistent explanation for the whole set of data, indicating ? = (3.6 ± 0.2) meV and a ratio 2?/KBTC ? 3.5 ± 0.2. In particular, point contact characteristics showing gap-like features at higher voltages have been interpreted by considering the formation of an intergrain Josephson junction in series with the point contact junction. Further confirm..
Study of the pairing symmetry in the electron-doped cuprate Pr(1-x)LaCe(x)CuO(4-y) by tunneling spectroscopy
No full textWe performed Point Contact Andreev Reflection Spectroscopy experiments on Pr(1-x)Lace(x)CuO(4-y) crystals. The variety of the measured spectra are all explained in terms of a modified BTK model considering a d-wave symmetry of the superconducting order parameter. We give an estimation of the energy gap Delta = (3.5 +/- 0.2) meV and of the ratio 2 Delta/k(B)T(c) similar or equal to 3.6 +/- 0.3. We measured the temperature evolution of the dl/dV vs. V characteristics and we extracted a conventional BCS temperature dependence of the superconducting energy gap. Finally, in order to explain the conductance spectra showing higher voltage gap-like features we consider a model in which the formation of a Josephson junction in series with the Point Contact junction is realized due to the tip pressure. (C) 2010 Elsevier B.V. All rights reserved
Imaging the spontaneous formation of vortex-antivortex pairs in planar superconductor/ferromagnet hybrid structures.
No full textLow-temperature magnetic force microscopy has been used to visualize spontaneous formation of vortexantivortex
pairs in hybrid ferromagnet/superconductor systems. Vortex-antivortex pairs are induced by the periodic
stray field of the ferromagnet. We find general equilibrium conditions for which spontaneous vortex-antivortex
pairs are formed during zero-field cooling of the hybrid ferromagnet/superconductor bilayers. Vortices can be
generated by the ferromagnet domains in the absence of an external field and they are thermodynamically stable
for values of the stray field and the period of the stripe magnetic domains that exceed a certain threshold
Point contact spectroscopy on electron doped Pr(1-x)LaCe(x)CuO(4-y)
No full textPoint contact spectroscopy has been used to address the question of the symmetry of the order parameter in the superconducting Pr(1-x)LaCe(x)CuO(4-y) compound. We recorded a huge variety of data that were consistently interpreted by considering a d-wave symmetry of the superconducting order parameter. Despite the different features appearing in the tunneling conductance spectra, all data inferred a superconducting energy gap amplitude. Delta similar or equal to 3.6 +/- 0.2 meV, with a conventional BCS temperature dependence and a ratio 2 Delta/K(B)T(c) similar or equal to 3.5 +/- 0.2. Also for the rare contacts showing a smaller gap value Delta similar or equal to 2.0 meV we found the same BCS ratio confirming that we are probing a sample area with reduced superconductivity (T(c) similar or equal to 14K). (C) 2009 Elsevier B.V. All rights reserved
Adsorption Behavior of Asymmetric Pd Pincer Complexes on a Cu(111) Surface
Full text linkWe address the adsorption of asymmetric Pd pincer complexes on a Cu(111) surface by scanning tunneling microscopy. The structural asymmetry is manifested in the observation of two chiral enantiomers. To enable an unambiguous identification of individual constituents, three closely related complexes with small modifications are investigated in parallel. Thereby, methyl substituents determine attractive molecule-molecule interaction. Depending on their distribution, dimerization and tetramerization can be observed
Scanning tunneling microscope study of iron(II) phthalocyanine growth on metals and insulating surfaces
Full text linkThe growth behavior of iron(II) phthalocyanine (FePc) molecules on Cu(111) and on NaCl/Cu(111) surfaces has been studied by a variable-temperature scanning tunneling microscope. Upon deposition at room temperature, FePc molecules with different adsorption configurations form short-ranged ordered domains on Cu(111). In the second FePc monolayer long-range ordering is observed. Molecule–molecule and molecule–substrate interactions are discussed in comparison with previous findings for FePc on Au(111). In order to reduce molecule–substrate interaction insulating NaCl layers are introduced. FePc molecules adsorb on Cl- anion sites but show high mobility during preparation. Our results provide detailed insight into the growth behavior of organic molecules on metallic and insulating surfaces
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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