1,721,062 research outputs found
Quantum anomalous Hall effect in time-reversal-symmetry breaking topological insulators
No full textThe quantum anomalous Hall effect (QAHE), the last member of Hall family, was predicted to exhibit quantized Hall conductivity αyx= e2/h without any external magnetic field. The QAHE shares a similar physical phenomenon with the integer quantum Hall effect (QHE), whereas its physical origin relies on the intrinsic topological inverted band structure and ferromagnetism. Since the QAHE does not require external energy input in the form of magnetic field, it is believed that this effect has unique potential for applications in future electronic devices with low-power consumption. More recently, the QAHE has been experimentally observed in thin films of the time-reversal symmetry breaking ferromagnetic (FM) topological insulators (TI), Cr- and V- doped (Bi,Sb)2Te3. In this topical review, we review the history of TI based QAHE, the route to the experimental observation of the QAHE in the above two systems, the current status of the research of the QAHE, and finally the prospects for future studies.United States. Department of Energy. Office of Basic Energy Sciences (Award DE-SC0001299)United States. Department of Energy. Office of Basic Energy Sciences (Award DE-FG02-09ER46577
Two-Dimensional Heterojunction Interlayer Tunneling Field Effect Transistors (Thin-TFETs)
Full text linkLayered 2-D crystals embrace unique features of atomically thin bodies, dangling bond free
interfaces, and step-like 2-D density of states. To exploit these features for the design of a steep slope
transistor, we propose a Two-dimensional heterojunction interlayer tunneling field effect transistor (Thin-
TFET), where a steep subthreshold swing (SS) of ∼14 mV/dec and a high on-current of ∼300 μA/μm are
estimated theoretically. The SS is ultimately limited by the density of states broadening at the band edges
and the on-current density is estimated based on the interlayer charge transfer time measured in recent
experimental studies. To minimize supply voltage VDD while simultaneously maximizing on currents,
Thin-TFETs are best realized in heterostructures with near broken gap energy band alignment. Using
the WSe2/SnSe2 stacked-monolayer heterostructure, a model material system with desired properties for Thin-TFETs, the performance of both n-type and p-type Thin-TFETs is theoretically evaluated. Nonideal effects such as a nonuniform van der Waals gap thickness between the two 2-D semiconductors and finite total access resistance are also studied. Finally, we present a benchmark study for digital applications, showing the Thin-TFETs may outperform CMOS and III–V TFETs in term of both switching speed and energy consumption at low-supply voltages
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
Hydration-dependent dynamic crossover phenomenon in protein hydration water
Full text linkThe characteristic relaxation time τ of protein hydration water exhibits a strong hydration level h dependence. The dynamic crossover is observed when h is higher than the monolayer hydration level h[subscript c] =0.2–0.25 and becomes more visible as h increases. When h is lower than h[subscript c], τ only exhibits Arrhenius behavior in the measured temperature range. The activation energy of the Arrhenius behavior is insensitive to h, indicating a local-like motion. Moreover, the h dependence of the crossover temperature shows that the protein dynamic transition is not directly or solely induced by the dynamic crossover in the hydration water.United States. Dept. of Energy. Office of Basic Energy Sciences (Contract DE-FG02-90ER45429
Topological semimetal to insulator quantum phase transition in the Zintl compounds Ba2X(X = Si,Ge)
Full text linkBy first-principles calculations, we find that Ba[subscript 2]X(X=Si,Ge) hosts a topological semimetal phase with one nodal ring in the k[subscript x]=0 plane, which is protected by the glide mirror symmetry when spin-orbit coupling (SOC) is ignored. The corresponding drumheadlike surface flat band appears on the (100) surface in surface Green's function calculation. Furthermore, a topological-semimetal-to-insulator transition is found. The nodal line semimetal would evolve into a topological insulator as SOC is turned on. The topologically protected metallic surface states emerge around the [bar over]Γ point, which could be tuned into the topologically trivial insulator state by more than 3% hydrostatic strain. These results reveal a category of materials showing quantum phase transition between topological semimetal and insulator, and tunability through elastic strain engineering.National Basic Research Program of China (973 Program) (Contract 2012CB619402)Xi’an Jiaotong University. 985 ProjectNational Science Foundation (U.S.) (Grant DMR-1410636)Solid-State Solar-Thermal Energy Conversion CenterUnited States. Dept. of Energy. Office of Basic Energy Sciences (Award DE-SC0001299/DE-FG02- 09ER46577
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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