1,720,979 research outputs found
Colossal orbital-Edelstein effect in non-centrosymmetric superconductors
Full text linkIn superconductors that lack inversion symmetry, the flow of supercurrent can
induce a non-vanishing magnetization, a phenomenon which is at the heart of
non-dissipative magneto-electric effects, also known as Edelstein effects. For
electrons carrying spin and orbital moments a question of fundamental relevance
deals with the orbital nature of magneto-electric effects in conventional
spin-singlet superconductors with Rashba coupling. Remarkably, we find that the
supercurrent-induced orbital magnetization is more than one order of magnitude
greater than that due to the spin, giving rise to a colossal magneto-electric
effect. The induced orbital magnetization is shown to be sign tunable, with the
sign change occurring for the Fermi level lying in proximity of avoiding
crossing points in the Brillouin zone and in the presence of superconducting
phase inhomogeneities, yielding domains with opposite orbital moment
orientation. The orbital-dominated magneto-electric phenomena, hence, have
clear-cut marks for detection both in the bulk and at the edge of the system
and are expected to be a general feature of multi-orbital superconductors
without inversion symmetry breaking.Comment: 7 pages, 5 figure
Frustration-driven Josephson phase dynamics
No full textThe Josephson equations predict remarkable effects concerning the phase state of a superconducting junction with an oscillating current induced by a static voltage. Whether the paradigm can be twisted by yielding an oscillating voltage without making use of harmonic drives is a fundamentally relevant problem yet not fully settled. Here, we demonstrate that a dynamical regime with an oscillating phase evolution is a general hallmark of driven Josephson systems exhibiting sign competition in the Josephson couplings. We show that in frustrated Josephson systems an oscillating phase dynamics gets switched on by driving the changeover among different ground states, which can be induced by varying the parameters that set the phase state. Remarkably, the character of the transitions in the Josephson phase space allows different types of dynamics, with few or several harmonics. This result sets out a characteristic mark of any superconducting system with frustrated Josephson couplings and can be exploited to disentangle the complexity of the underlying phases
Spin and orbital Edelstein effect in spin-orbit coupled noncentrosymmetric superconductors
No full textSuperconductors without inversion symmetry can exhibit a nonzero magnetization when a supercurrent is present, leading to nondissipative magnetoelectric effects. Here, we focus on understanding the relation between the spin and orbital properties of these effects in spin-singlet noncentrosymmetric superconductors with orbital Rashba coupling. Our findings indicate that the correlation between spin and orbital moments induced by supercurrents is generally not determined by the sign of atomic spin-orbit coupling but rather by the number of bands at the Fermi level and the orbital characteristics of those bands with respect to the mirror parity. The outcomes demonstrate that the sign change of the orbital Edelstein effect near avoiding crossing bands remains robust despite modifications to the atomic spin-orbit amplitude. Furthermore, we observe that the spin Edelstein effect is typically one order of magnitude smaller than the orbital Edelstein effect, but can be significantly enhanced in certain scenarios with increased atomic spin-orbit coupling
Theory of integer quantum Hall polaritons in graphene
No full textWe present a theory of the cavity quantum electrodynamics of the graphene cyclotron resonance. By employing a canonical transformation, we derive an effective Hamiltonian for the system comprising two neighboring Landau levels dressed by the cavity electromagnetic field (integer quantum Hall polaritons). This generalized Dicke Hamiltonian, which contains terms that are quadratic in the electromagnetic field and respects gauge invariance, is then used to calculate thermodynamic properties of the quantum Hall polariton system. Finally, we demonstrate that the generalized Dicke description fails when the graphene sheet is heavily doped, i.e., when the Landau level spectrum of two-dimensional massless Dirac fermions is approximately harmonic. In this case we >integrate out> the Landau levels in valence band and obtain an effective Hamiltonian for the entire stack of Landau levels in conduction band, as dressed by strong light-matter interactions. © 2014 American Physical Society.We acknowledge support by the EC under Graphene Flagship (Contract No. CNECT-ICT-604391) (M.P.), the European Research Council Advanced Grant (Contract No. 290846) (L.C.), the Italian Ministry of Education, University, and Research (MIUR) through the programs “FIRB IDEAS”–Project ESQUI (Grant No. RBID08B3FM) (V.G.), “FIRB—Futuro in Ricerca 2010”—Project PLASMOGRAPH (Grant No. RBFR10M5BT) (M.P.) and PRIN Grant No. 2010LLKJBX (R.F.), and a 2012 SNS Internal Project (V.G.).Peer Reviewe
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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