scholarly journals Linear Response in Topological Materials

2019 ◽  
Vol 9 (22) ◽  
pp. 4832 ◽  
Author(s):  
Jonathan Noky ◽  
Yan Sun
Keyword(s):  
Band Structure ◽  
Linear Response ◽  
Point Of View ◽  
New Materials ◽  
Symmetry Point ◽  
Berry Curvature ◽  
Topological Materials ◽  
Electromagnetic Responses ◽  
Potential Applications ◽  
New Perspective

The discovery of topological insulators and semimetals has opened up a new perspective to understand materials. Owing to the special band structure and enlarged Berry curvature, the linear responses are strongly enhanced in topological materials. The interplay of topological band structure and symmetries plays a crucial role for designing new materials with strong and exotic new electromagnetic responses and provides promising mechanisms and new materials for the next generation of technological applications. We review the fundamental concept of linear responses in topological materials from the symmetry point of view and discuss their potential applications.

scholarly journals Topologically Protected Edge State in Two-Dimensional Su–Schrieffer–Heeger Circuit

Research ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Shuo Liu ◽  
Wenlong Gao ◽  
Qian Zhang ◽  
Shaojie Ma ◽  
Lei Zhang ◽  
...  
Keyword(s):  
Band Structure ◽  
Edge State ◽  
Edge States ◽  
Exciting Field ◽  
Circuit Performance ◽  
Topological Materials ◽  
Full Control ◽  
Potential Applications ◽  
Physical Phenomena ◽  
Gap Width

Topological circuits, an exciting field just emerged over the last two years, have become a very accessible platform for realizing and exploring topological physics, with many of their physical phenomena and potential applications as yet to be discovered. In this work, we design and experimentally demonstrate a topologically nontrivial band structure and the associated topologically protected edge states in an RF circuit, which is composed of a collection of grounded capacitors connected by alternating inductors in the x and y directions, in analogy to the Su–Schrieffer–Heeger model. We take full control of the topological invariant (i.e., Zak phase) as well as the gap width of the band structure by simply tuning the circuit parameters. Excellent agreement is found between the experimental and simulation results, both showing obvious nontrivial edge state that is tightly bound to the circuit boundaries with extreme robustness against various types of defects. The demonstration of topological properties in circuits provides a convenient and flexible platform for studying topological materials and the possibility for developing flexible circuits with highly robust circuit performance.

scholarly journals Unraveling materials Berry curvature and Chern numbers from real-time evolution of Bloch states

2019 ◽  
Vol 116 (10) ◽  
pp. 4135-4140 ◽  
Author(s):  
Dongbin Shin ◽  
Shunsuke A. Sato ◽  
Hannes Hübener ◽  
Umberto De Giovannini ◽  
Jeongwoo Kim ◽  
...  
Keyword(s):  
Real Time ◽  
Linear Response ◽  
Quantum Spin ◽  
Topological Properties ◽  
Berry Curvature ◽  
Topological Materials ◽  
Chern Numbers ◽  
Nonequilibrium States ◽  
Topological Characteristics ◽  
Topological Character

Materials can be classified by the topological character of their electronic structure and, in this perspective, global attributes immune to local deformations have been discussed in terms of Berry curvature and Chern numbers. Except for instructional simple models, linear response theories have been ubiquitously used in calculations of topological properties of real materials. Here we propose a completely different and versatile approach to obtain the topological characteristics of materials by calculating physical observables from the real-time evolving Bloch states: The cell-averaged current density reveals the anomalous velocities that lead to the conductivity quantum. Results for prototypical cases are shown, including a spin-frozen valley Hall and a quantum anomalous Hall insulator. The advantage of this method is best illustrated by the example of a quantum spin Hall insulator: The quantized spin Hall conductivity is straightforwardly obtained irrespective of the non-Abelian nature in its Berry curvature. Moreover, the method can be extended to the description of real observables in nonequilibrium states of topological materials.

ON THE RELATIONSHIP BETWEEN PARAMETRIC VARIATION AND STATE FEEDBACK IN CHAOS CONTROL

2002 ◽  
Vol 12 (06) ◽  
pp. 1411-1415 ◽  
Author(s):  
ZENGRONG LIU ◽  
GUANRONG CHEN
Keyword(s):  
Chaos Synchronization ◽  
State Feedback ◽  
Chaos Control ◽  
Point Of View ◽  
Form Analysis ◽  
Parametric Variation ◽  
Potential Applications ◽  
New Perspective ◽  
First Time ◽  
The Relationship

In this Letter, we study the popular parametric variation chaos control and state-feedback methodologies in chaos control, and point out for the first time that they are actually equivalent in the sense that there exist diffeomorphisms that can convert one to the other for most smooth chaotic systems. Detailed conversions are worked out for typical discrete chaotic maps (logistic, Hénon) and continuous flows (Rösller, Lorenz) for illustration. This unifies the two seemingly different approaches from the physics and the engineering communities on chaos control. This new perspective reveals some new potential applications such as chaos synchronization and normal form analysis from a unified mathematical point of view.

scholarly journals Topologically Protected Edge State in Two-Dimensional Su–Schrieffer–Heeger Circuit

Research ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Shuo Liu ◽  
Wenlong Gao ◽  
Qian Zhang ◽  
Shaojie Ma ◽  
Lei Zhang ◽  
...  
Keyword(s):  
Band Structure ◽  
Edge State ◽  
Edge States ◽  
Exciting Field ◽  
Circuit Performance ◽  
Topological Materials ◽  
Full Control ◽  
Potential Applications ◽  
Physical Phenomena ◽  
Gap Width

Topological circuits, an exciting field just emerged over the last two years, have become a very accessible platform for realizing and exploring topological physics, with many of their physical phenomena and potential applications as yet to be discovered. In this work, we design and experimentally demonstrate a topologically nontrivial band structure and the associated topologically protected edge states in an RF circuit, which is composed of a collection of grounded capacitors connected by alternating inductors in the x and y directions, in analogy to the Su–Schrieffer–Heeger model. We take full control of the topological invariant (i.e., Zak phase) as well as the gap width of the band structure by simply tuning the circuit parameters. Excellent agreement is found between the experimental and simulation results, both showing obvious nontrivial edge state that is tightly bound to the circuit boundaries with extreme robustness against various types of defects. The demonstration of topological properties in circuits provides a convenient and flexible platform for studying topological materials and the possibility for developing flexible circuits with highly robust circuit performance.

Short Review and opinion: New matter properties and applications based on Hybrids Graphene based Metamaterials

2020 ◽  
Vol 04 ◽  
Author(s):  
A. Guillermo Bracamonte
Keyword(s):  
Short Review ◽  
New Materials ◽  
Design And Synthesis ◽  
Chemical Structures ◽  
Current State ◽  
Potential Applications ◽  
Fundamental Research ◽  
Miniaturized Instrumentation ◽  
And Control ◽  
Conductive Properties

: Graphene as Organic material showed special attention due to their electronic and conductive properties. Moreover, its highly conjugated chemical structures and relative easy modification permitted varied design and control of targeted properties and applications. In addition, this Nanomaterial accompanied with pseudo Electromagnetic fields permitted photonics, electronics and Quantum interactions with their surrounding that generated new materials properties. In this context, this short Review, intends to discuss many of these studies related with new materials based on graphene for light and electronic interactions, conductions, and new modes of non-classical light generation. It should be highlighted that these new materials and metamaterials are currently in progress. For this reason it was showed and discussed some representative examples from Fundamental Research with Potential Applications as well as for their incorporations to real Advanced devices and miniaturized instrumentation. In this way, it was proposed this Special issue entitled “Design and synthesis of Hybrids Graphene based Metamaterials”, in order to open and share the knowledge of the Current State of the Art in this Multidisciplinary field.

scholarly journals Interface-induced sign reversal of the anomalous Hall effect in magnetic topological insulator heterostructures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Fei Wang ◽  
Xuepeng Wang ◽  
Yi-Fan Zhao ◽  
Di Xiao ◽  
Ling-Jie Zhou ◽  
...  
Keyword(s):  
Hall Effect ◽  
Electric Fields ◽  
First Principles ◽  
Berry Phase ◽  
Condensed Matter ◽  
Anomalous Hall Effect ◽  
First Principles Calculations ◽  
Sign Reversal ◽  
Berry Curvature ◽  
Topological Materials

AbstractThe Berry phase picture provides important insights into the electronic properties of condensed matter systems. The intrinsic anomalous Hall (AH) effect can be understood as the consequence of non-zero Berry curvature in momentum space. Here, we fabricate TI/magnetic TI heterostructures and find that the sign of the AH effect in the magnetic TI layer can be changed from being positive to negative with increasing the thickness of the top TI layer. Our first-principles calculations show that the built-in electric fields at the TI/magnetic TI interface influence the band structure of the magnetic TI layer, and thus lead to a reconstruction of the Berry curvature in the heterostructure samples. Based on the interface-induced AH effect with a negative sign in TI/V-doped TI bilayer structures, we create an artificial “topological Hall effect”-like feature in the Hall trace of the V-doped TI/TI/Cr-doped TI sandwich heterostructures. Our study provides a new route to create the Berry curvature change in magnetic topological materials that may lead to potential technological applications.

scholarly journals Composite Poly(vinyl alcohol)-Based Nanofibers Embedding Differently-Shaped Gold Nanoparticles: Preparation and Characterization

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1604
Author(s):  
Andrea Dodero ◽  
Maila Castellano ◽  
Paola Lova ◽  
Massimo Ottonelli ◽  
Elisabetta Brunengo ◽  
...  
Keyword(s):  
Vinyl Alcohol ◽  
Ad Hoc ◽  
Chemical Reduction ◽  
Chemical Properties ◽  
Single Step ◽  
Gold Nanostructures ◽  
Poly Vinyl Alcohol ◽  
Spherical Nanoparticles ◽  
Potential Applications ◽  
New Perspective

Poly(vinyl alcohol) nanofibrous mats containing ad hoc synthesized gold nanostructures were prepared via a single-step electrospinning procedure and investigated as a novel composite platform with several potential applications. Specifically, the effect of differently shaped and sized gold nanostructures on the resulting mat physical-chemical properties was investigated. In detail, nearly spherical nanoparticles and nanorods were first synthesized through a chemical reduction of gold precursors in water by using (hexadecyl)trimethylammonium bromide as the stabilizing agent. These nanostructures were then dispersed in poly(vinyl alcohol) aqueous solutions to prepare nanofibrous mats, which were then stabilized via a humble thermal treatment able to enhance their thermal stability and water resistance. Remarkably, the nanostructure type was proven to influence the mesh morphology, with the small spherical nanoparticles and the large nanorods leading to thinner well defined or bigger defect-rich nanofibers, respectively. Finally, the good mechanical properties shown by the prepared composite mats suggest their ease of handleability thereby opening new perspective applications.

TRADITION AND INNOVATION IN MODERN KAZAKH POETRY (XX century and independence)

2021 ◽  
Vol 76 (2) ◽  
pp. 118-128
Author(s):  
Sh. Kuttybaev ◽  
◽  
Е. Abdimomynov ◽  
Keyword(s):  
20Th Century ◽  
Large Scale ◽  
Point Of View ◽  
Soviet Period ◽  
Evolutionary Development ◽  
Spiritual Values ◽  
Literary Traditions ◽  
New Perspective ◽  
National Poetry ◽  
In The Beginning

The article analyzes views on innovation in the literary science of the early twentieth century and the work of Alash representatives in an era that is a period filled with profound changes and large-scale innovations in Kazakh society. In addition, works related to freedom, enlightenment, politics, spiritual values, the position of the people as a whole and social changes are considered the idea of independence and continuity. On the way of evolutionary development of the Kazakh literature, artistic power, thematic and ideological character, substantial and stylistic features of poetry of poets in the beginning of the XX century and during the Great Patriotic War, in subsequent years and years of independence are discussed in detail. In addition, on the basis of literary traditions and novelty, the works of prominent poets of Kazakh poetry of the 20th century and Independence are considered and comprehensively characterized, i.e. internal motives, the content of life phenomena in national poetry are analyzed in close connection with the works of poets. The original vision of the traditional and differentiated in the literature of the Soviet period in the works of poets from a new perspective, from the point of view of today. In addition, the works of outstanding poets of Kazakh poetry in the period of the 20th century and independence are considered on the basis of classical tradition and novelty in literature.

scholarly journals Difficulty in implementing continuous improvement – Rasch measurement analysis

2019 ◽  
Vol 25 (6) ◽  
pp. 1228-1250 ◽  
Author(s):  
Lidia Sanchez-Ruiz ◽  
Beatriz Blanco ◽  
Emma Diaz
Keyword(s):  
Continuous Improvement ◽  
Measurement Theory ◽  
Reliability And Validity ◽  
Rasch Measurement ◽  
Point Of View ◽  
Future Research ◽  
Theoretical Point ◽  
Content Type ◽  
Level Of Difficulty ◽  
New Perspective

Purpose The purpose of this paper is to define a general and common construct in order to measure the level of difficulty companies experience when they implement continuous improvement (CI). Additionally, a rank of barriers is obtained together with a rank of companies. Design/methodology/approach In order to achieve the objective, first, a literature review is carried out to specify the domain of the construct; second, a sample of items is selected; third a survey is carried out in companies that have already implemented CI initiatives, the results being thus limited to this population; fourth, measures are purified by analysing the reliability and validity of the measurements, and finally results are obtained. The Rasch measurement theory will be used to provide a new perspective on a mature research topic. Findings It can be concluded that a new valid construct has been defined together with a rank of CI barriers, being lack of time the main barrier. A rank of companies is also obtained which is a first step in the development of future research studies. Practical implications Managers are provided with a better understanding of the barriers that can obstruct CI implementation. Thus, the rank of CI barriers guides managers through the most common and important obstacles so that they will be able to plan better CI strategies. In addition, the rank of companies allows each company to undertake a benchmarking exercise. Originality/value This work proposes a new way of analysing the difficulty in implementing CI as a continuum, rather than as independent barriers. From a theoretical point of view, it defines a new construct and offers a rank of CI barriers together with a rank of companies based on their level of difficulty when implementing CI initiatives. This is something new, as previous studies were mainly focussed on the items side. From a practical point of view, this study offers the surveyed companies the opportunity to see how they are positioned with respect to the other companies. Moreover, this rank of companies is the foundation on which to develop further studies with a practical orientation in the future.

scholarly journals A CRITICAL ANALYSIS OF THE COSMOLOGICAL IMPLEMENTATION OF LOOP QUANTUM GRAVITY

2012 ◽  
Vol 27 (07) ◽  
pp. 1250032 ◽  
Author(s):  
FRANCESCO CIANFRANI ◽  
GIOVANNI MONTANI
Keyword(s):  
Quantum Gravity ◽  
Quantum Cosmology ◽  
Loop Quantum Gravity ◽  
Critical Discussion ◽  
Point Of View ◽  
Graph Structure ◽  
Quantum Geometry ◽  
Cosmological Problem ◽  
New Perspective ◽  
Made In

This papers offers a critical discussion on the procedure by which Loop Quantum Cosmology (LQC) is constructed from the full Loop Quantum Gravity (LQG) theory. Revising recent issues in preserving SU(2) symmetry when quantizing the isotropic Universe, we trace a new perspective in approaching the cosmological problem within quantum geometry. The cosmological sector of LQG is reviewed and a critical point of view on LQC is presented. It is outlined how a polymer-like scale for quantum cosmology can be predicted from a proper fundamental graph underlying the homogeneous and isotropic continuous picture. However, such a minimum scale does not coincide with the choice made in LQC. Finally, the perspectives towards a consistent cosmological LQG model based on such a graph structure are discussed.

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