1,721,623 research outputs found
Nonequilibrium Josephson and Andreev current through interacting quantum dots
No full textWe present a theory of transport through interacting quantum dots coupled to normal and superconducting leads in the limit of weak tunnel coupling. A Josephson current between two superconducting leads, carried by first-order tunnel processes, can be established by the nonequilibrium proximity effect. Both the Andreev and the Josephson currents are suppressed for bias voltages below a threshold set by the Coulomb charging energy. A pi-transition of the supercurrent can be driven by tuning gate or bias voltages
Real-time diagrammatic approach to transport through interacting quantum dots with normal and superconducting leads
No full textWe present a real-time diagrammatic theory for transport through interacting quantum dots tunnel coupled to normal and superconducting leads. Our formulation describes both the equilibrium and nonequilibrium superconducting proximity effects in a quantum dot. We study a three-terminal transistor geometry, consisting of a single-level quantum dot tunnel coupled to two phase-biased superconducting leads and one voltage-biased normal lead. We compute both the Josephson current between the two superconductors and the Andreev current in the normal lead, and analyze their switching on and off as well as transitions between 0 and pi states as a function of gate and bias voltages. For the limit of large superconducting gaps in the leads, we describe the formation of Andreev bound states within an exact resummation of all orders in the tunnel coupling to the superconducting leads, and we discuss their signature in the nonequilibrium Josephson and Andreev currents and the quantum-dot charge
Comment on "Do intradot electron-electron interactions induce dephasing"?
No full textA Comment on the Letter by Zhao-tan Jiang etal., Phys. Rev. Lett.PRLTAO0031-9007 93, 076802 (2004)10.1103/PhysRevLett.93.076802. The authors of the Letter offer a Reply. © 2005 The American Physical Society
Coulomb-interaction effects in full counting statistics of a quantum-dot Aharonov-Bohm interferometer
No full textWe study the effect of Coulomb interaction on the full counting statistics of an Aharonov-Bohm (AB) interferometer with a single-level quantum dot in one arm in the regime of weak dot-lead and lead-lead tunnel couplings. In the absence of Coulomb interaction, the interference processes are of nonresonant nature with an even AB flux dependence and obey bidirectional Poissonian statistics. For large charging energy, the statistic of these processes changes. In addition, processes of resonant nature with an odd flux dependence appear. In the limit of strongly asymmetric tunnel couplings from the dot to the left and right leads, their statistics is found to be strongly super-Poissonian
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Superconducting proximity effect in interacting double-dot systems
No full textWe study subgap transport from a superconductor through a double quantum dot with large on-site Coulomb repulsion to two normal leads. Nonlocal superconducting correlations in the double dot are induced by the proximity to the superconducting lead, detectable in nonlocal Andreev transport that splits Cooper pairs in locally separated, spin-entangled electrons. We find that the I-V characteristics are strongly asymmetric: for a large bias voltage of certain polarity, transport is blocked by populating the double dot with states whose spin symmetry is incompatible with the superconductor. Furthermore, by tuning gate voltages one has access to splitting of the Andreev excitation energies, which is visible in the differential conductance
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