1,720,982 research outputs found
Electrically Tunable Superconductivity Through Surface Orbital Polarization
Full text linkWe investigate the physical mechanisms for achieving an electrical control of conventional spin-singlet superconductivity in thin films by focusing on the role of surface orbital polarization. Assuming a multiorbital description of the metallic state, due to screening effects the electric field acts by modifying the strength of the surface potential and, in turn, yields nontrivial orbital Rashba couplings. The resulting orbital polarization at the surface and in its close proximity is shown to have a dramatic impact on superconductivity. We demonstrate that, by varying the strength of the electric field, the superconducting phase can be either suppressed, i.e., turned into normal metal, or undergo a 0-π transition with the π phase being marked by nontrivial sign change of the superconducting order parameter between different bands. These findings unveil a rich scenario to design heterostructures with superconducting orbitronics effects
Computation of transient dynamics of energy power for a dissipative two state system
No full textWe consider a two-level system coupled to a thermal bath and we investigate the variation of energy transferred to the reservoir as a function of time. The physical quantity under investigation is the time-dependent quantum average power. We compare quantum master equation approaches with the functional influence method. Differences and similarities between the methods are analysed, showing deviations at low temperature between the functional integral approach and the predictions based on master equations
Quantum gradient evaluation through quantum non-demolition measurements
Full text linkWe discuss a Quantum Non-Demolition Measurement (QNDM) protocol to estimate
the derivatives of a cost function with a quantum computer. %This is a key step
for the implementation of variational quantum circuits. The cost function,
which is supposed to be classically hard to evaluate, is associated with the
average value of a quantum operator. Then a quantum computer is used to
efficiently extract information about the function and its derivative by
evolving the system with a so-called variational quantum circuit. To this aim,
we propose to use a quantum detector that allows us to directly estimate the
derivatives of an observable, i.e., the derivative of the cost function. With
respect to the standard direct measurement approach, this leads to a reduction
of the number of circuit iterations needed to run the variational quantum
circuits. The advantage increases if we want to estimate the higher-order
derivatives. We also show that the presented approach can lead to a further
advantage in terms of the number of total logical gates needed to run the
variational quantum circuits. These results make the QNDM a valuable
alternative to implementing the variational quantum circuits
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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