1,720,976 research outputs found
Ordering and multiple phase transitions in ultrathin nickelate superlattices
No full textWe interpret via advanced ab initio calculations the multiple phase transitions observed recently in ultrathin LaNiO3/LaAlO3 superlattices. The ground state is insulating, weakly charge ordered, and antiferromagnetic due to concurrent structural distortion and weak valency disproportionation. We infer distinct transitions around 50 K and 110 K, respectively, from antiferromagnetic order to moment disorder, and from a structurally dimerized insulator to an undistorted metallic Pauli paramagnet (exhibiting a cupratelike Fermi surface). The results are in satisfactory agreement with experimental results
Jahn-Teller stabilization of magnetic and orbital ordering in rocksalt CuO
No full textSelf-interaction-corrected local-density-functional calculations show that rocksalt-structure CuO spontaneously becomes insulating and magnetically ordered by tetragonal Jahn-Teller distortion of Cu-centered octahedra. The equilibrium structure is axially expanded by 9%, has a charge-transfer gap of 1.1 eV, and antiferromagnetic ordering-II with a d(x2-y2) spin-polarized hole and a Neel temperature of 530 K within the anisotropic Ising model
Fermi-surface pockets in YBa2Cu3O6.5: Comparison of ab initio techniques
No full textWe study the Fermi surface of metallic, nonmagnetic ortho-II YBa2Cu3O6.5 using three different density-functional-based band-structure techniques [generalized gradient approximation (GGA), GGA+U, and pseudo-self-interaction correction (PSIC)]. The calculated Fermi surface exhibits no pockets in GGA+U and PSIC, and a minor one in GGA. Upon shifting the Fermi level in the vicinity of the calculated value, we instead observe several pocket structures. We calculate their cross-sectional areas and cyclotron masses. Overall, our calculations show no solid evidence of the existence of electronlike-nor, in fact, of any-Fermi-surface pockets in this phase. This suggests that the origin of the pockets should be sought for in other different phases
Fermi-surface pockets in magnetic underdoped cuprates from first principles
No full textUsing an innovative first-principles band theory enabling the exploration of Mott-insulating magnetic cuprates, we study the Fermi surface of underdoped Y(1-x)Ca(x)Ba(2)Cu(3)O(6) in a selection of magnetically ordered and polaronic states. Inclusion of doping on the antiferromagnetically ordered CuO(2) planes causes the appearance of small, hole-like Fermi-surface pockets centered around the nodal points. The pocket properties (area, mass) depend on the underlying magnetic ordering (e.g. change with polaron formation), although the hole-like character is rather persistent for all the examined magnetic states. Copyright (C) EPLA, 200
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
Design of a Mott Multiferroic from a Nonmagnetic Polar Metal
No full textWe examine the electronic properties of the newly discovered "ferroelectric metal" LiOsO3 combining density-functional and dynamical mean-field theories. We show that the material is close to a Mott transition and that electronic correlations can be tuned to engineer a Mott multiferroic state in the 1/1 superlattice of LiOsO3 and LiNbO3. We use electronic structure calculations to predict that the (LiOsO3)1/(LiNbO3)1 superlattice exhibits strong coupling between magnetic and ferroelectric degrees of freedom with a ferroelectric polarization of 41.2 μC cm-2, Curie temperature of 927 K, and Néel temperature of 379 K. Our results support a route towards high-temperature multiferroics, i.e., driving nonmagnetic polar metals into correlated insulating magnetic states
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
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