1,721,005 research outputs found
Cavity quantum electrodynamical Chern insulator: Towards light-induced quantized anomalous Hall effect in graphene
Full text linkWe show that an energy gap is induced in graphene by light-matter coupling to a circularly polarized photon mode in a cavity. Using many-body perturbation theory, we compute the electronic spectra which exhibit photon-dressed sidebands akin to Floquet sidebands for laser-driven materials. In contrast with Floquet topological insulators, in which a strictly quantized Hall response is induced by light only for off-resonant driving in the high-frequency limit, the photon-dressed Dirac fermions in the cavity show a quantized Hall response characterized by an integer Chern number. Specifically for graphene, we predict that a Hall conductance of 2e2/h can be induced in the low-temperature limit
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
Cavitronics in Low-Dimensional Systems
Full text linkEigenschaften von Materialien mit Hilfe von Licht zu kontrollieren ist eine vielversprechende Forschungs-richtung im Gebiet der Physik kondensierter Materie. Als eine neue Möglichkeit dies zu erreichen wurde die Verwendung optischer Kavitäten, in denen die Freiheitsgrade von Licht und Materie hybridisiert wer-den, vorgeschlagen. In dieser Dissertation untersuchen wir das Potential solcher Kontrolle durch Kavitäten für niedrigdimensionale elektronische Systeme - daher der Titel der Arbeit, der zu Deutsch Kavitronik in niedrigdimensionalen Systemen lautet. Zu diesem Zweck schlagen wir ein exakt lösbares minimales Modell für Kavitronik vor. Hier wird die Änderung des elektromagnetischen Feldes innerhalb einer Kavität durch eine einzelne bosonische Mode beschrieben, analog zu paradigmatischen Modellen im verwandten Feld der Quanten Optik. Wir bestimmen den exakten Grundzustand des Modells und identifizieren Observablen, mit Hilfe derer sich starke Kopplung zwischen den Elektronen und dem elektromagnetischen Feld in Spektroskopie oder Leitfähigkeitsmessungen überprüfen lässt. In einem nächsten Schritt untersuchen wir die Validität der näherungsweisen Verwendung einer einzelnen Mode in unserem Modell. Hierfür rechnen wir die Massenänderung eines Elektrons in unterschiedlich gestalteten Kavitäten aus, wobei wir das gesamte kontinuierliche elektromagnetische Feld beschreiben. Unsere Ergebnisse zeigen, dass Kavitäten, die das Licht in Oberflächenmoden komprimieren, gut durch eine einzelne Mode beschrieben werden können. Zusätzlich diskutieren wir eine Vorschrift mit der man die phenomenologische Kopplung an so eine einzelne Mode ausrechnen kann. Wir erweitern im Folgenden das vorherige minimale Modell zu einem wechselwirkenden Modell und analysieren die Hybridisierung zwischen elektronischem System und Photonen in einer Kavität. Dabei identifizieren wir bestimmte Fluktuationen im elektronischen System, die eine entscheidende Rolle für diese Hybridisierung spielen. Als konkrete Anwendung erforschen wir die Möglichkeit Supraleitung mit Hilfe von optischen Kavitäten zu induzieren oder zu verstärken. Wir untersuchen die Auswirkung der Hybridisierung von optisch aktiven Phononen und Photonen, die sogenannte Polaritonen bilden, auf die Wechselwirkung, die durch die Phononen übertragen wird. Ergänzend hierzu schlagen wir einen neuen Mechanismus für Licht-induzierte Supraleitung vor. Dieser Mechanismus basiert auf einem Boson, zum Beispiel einem Photon, das an einen elektronischen Übergang koppelt. Wir konzeptionieren ein Experiment, bestehend aus einer Kavität, die Licht in einer Oberflächenmode einschließt, mit dem unsere Vorhersagen getestet werden können. Der Beitrag, den diese Arbeit leistet, um das Feld der Kavitronik zu konkreten experimentellen Anwendungen zu bewegen, lässt sich in drei Kategorien unterteilen: (i) Die Phenomenologie von Kavitronik wird in minimalen Modellen erforscht; (ii) diese Modelle werden mit einer realistischen Beschreibung des elektromagnetischen Feldes verbunden, um optimale experimentelle Bedingungen für die Kavitronik zu finden; und (iii)es werden experimentell überprüfbare Vorhersagen gemacht.Controlling material properties with light is a tantalizing goal of modern condensed matter physics. As a novel path to achieve this goal placing materials into optical cavities, effectively hybridizing light and matter degrees of freedom, has been put forward recently. In this thesis we explore the potential of such cavity engineering for low dimensional electronic systems – hence the term cavitronics. To this end we propose a minimal model for cavitronics. It accounts for the change of the electromagnetic field inside a cavity by coupling the electrons to a single bosonic mode in analogy to paradigmatic models in the related field of quantum optics. We find the exact ground state of the model and identify observables that allow the verification of strong coupling between the electrons and the photons of the cavity in spectroscopy or conductivity measurements. In a next step, we investigate the validity of single-mode models in the context of cavitronics. For this purpose we compute the mass change of itinerant electrons in different cavity setups taking the full continuum of modes of the electromagnetic field into account. Our results indicate the validity of a single mode approximation for describing the electromagnetic field confined in surface modes, such as in the case of surface phonon-polaritons. They further provide a recipe for obtaining the phenomenological light-matter coupling to that single mode. Extending our previous model to an interacting one, we analyze light-matter hybridization between electronic systems and photons in a cavity. We identify specific quantum fluctuations of the matter system to play a pivotal role for achieving such hybridization. As a concrete application we explore the propensity of an optical resonator to induce or enhance super-conductivity. We investigate how the hybridization of optically active phonons with the photons of a cavity, forming phonon-polaritons, affects their potential to mediate an effective attraction between the electrons. As an orthogonal route, we put forward a novel mechanism for photo-induced superconductivity. This mechanismis based on weak driving of a boson, such as a photon inside a cavity, coupling to an electronic transition. We propose a concrete and realizable experimental setup to test our predictions consisting of a cavity that confines light in a surface mode coupled to the two-dimensional material graphene. Through these points our work contributes to pushing the field of cavitronics towards concrete experimental realizations in a three-fold manner: (i) It establishes basic phenomenology of cavitronics in minimal models; (ii) connects these models to a realistic treatment of the electromagnetic field in order to identify ideal cavity setups; and (iii) makes experimentally testable predictions
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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