scholarly journals Boundary problems in cellular automata for topological insulators

2021 ◽  
Vol 2094 (2) ◽  
pp. 022079
Author(s):  
D P Fedchenko ◽  
V V Novikov ◽  
I V Timofeev
Keyword(s):  
Cellular Automata ◽  
Topological Insulator ◽  
Topological Insulators ◽  
Abstract Model ◽  
Boundary Problems

Abstract In physics, a topological insulator is a material that simultaneously exhibits the properties of a conductor on the surface and an insulator in the bulk. An abstract model of a twodimensional topological insulator is described in terms of tricolour cellular automata and excitations of a topological insulator are classified.

scholarly journals TOPOLOGICAL INSULATOR AND THE DIRAC EQUATION

SPIN ◽  
2011 ◽  
Vol 01 (01) ◽  
pp. 33-44 ◽  
Author(s):  
SHUN-QING SHEN ◽  
WEN-YU SHAN ◽  
HAI-ZHOU LU
Keyword(s):  
Dirac Equation ◽  
Topological Insulator ◽  
Bound States ◽  
Topological Insulators ◽  
Mass Term ◽  
Point Of View ◽  
Quadratic Term ◽  
General Description ◽  
Dirac Equations ◽  
Topological Quantum

We present a general description of topological insulators from the point of view of Dirac equations. The Z2 index for the Dirac equation is always zero, and thus the Dirac equation is topologically trivial. After the quadratic term in momentum is introduced to correct the mass term m or the band gap of the Dirac equation, i.e., m → m − Bp2, the Z2 index is modified as 1 for mB > 0 and 0 for mB < 0. For a fixed B there exists a topological quantum phase transition from a topologically trivial system to a nontrivial system when the sign of mass m changes. A series of solutions near the boundary in the modified Dirac equation is obtained, which is characteristic of topological insulator. From the solutions of the bound states and the Z2 index we establish a relation between the Dirac equation and topological insulators.

Proximity-induced magnetism and an anomalous Hall effect in Bi2Se3/LaCoO3: a topological insulator/ferromagnetic insulator thin film heterostructure

Nanoscale ◽  
2018 ◽  
Vol 10 (21) ◽  
pp. 10041-10049 ◽  
Author(s):  
Shanna Zhu ◽  
Dechao Meng ◽  
Genhao Liang ◽  
Gang Shi ◽  
Peng Zhao ◽  
...  
Keyword(s):  
Thin Film ◽  
Hall Effect ◽  
Topological Insulator ◽  
Topological Insulators ◽  
Anomalous Hall Effect ◽  
Ferromagnetic Phase ◽  
High Quality

A high-quality Bi2Se3/LaCoO3 heterostructure is fabricated as a new TI/FMI system for investigating a proximity-induced ferromagnetic phase in topological insulators.

scholarly journals Crystallinity of tellurium capping and epitaxy of ferromagnetic topological insulator films on SrTiO3

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Jihwey Park ◽  
Yeong-Ah Soh ◽  
Gabriel Aeppli ◽  
Xiao Feng ◽  
Yunbo Ou ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electronic Structure ◽  
Transport Properties ◽  
Topological Insulator ◽  
Topological Insulators ◽  
Surface States ◽  
Crystal Quality ◽  
X Rays ◽  
Capping Layer ◽  
Subtle Effect

Abstract Thin films of topological insulators are often capped with an insulating layer since topological insulators are known to be fragile to degradation. However, capping can hinder the observation of novel transport properties of the surface states. To understand the influence of capping on the surface states, it is crucial to understand the crystal structure and the atomic arrangement at the interfaces. Here, we use x-ray diffraction to establish the crystal structure of magnetic topological insulator Cr-doped (Bi,Sb)2Te3 (CBST) films grown on SrTiO3 (1 1 1) substrates with and without a Te capping layer. We find that both the film and capping layer are single crystal and that the crystal quality of the film is independent of the presence of the capping layer, but that x-rays cause sublimation of the CBST film, which is prevented by the capping layer. Our findings show that the different transport properties of capped films cannot be attributed to a lower crystal quality but to a more subtle effect such as a different electronic structure at the interface with the capping layer. Our results on the crystal structure and atomic arrangements of the topological heterostructure will enable modelling the electronic structure and design of topological heterostructures.

Simultaneous observation of surface- and edge-states of a 2D topological insulator through scanning tunneling spectroscopy and differential conductance imaging

2017 ◽  
Vol 19 (15) ◽  
pp. 9872-9878 ◽  
Author(s):  
Hrishikesh Bhunia ◽  
Abhijit Bar ◽  
Abhijit Bera ◽  
Amlan J. Pal
Keyword(s):  
Topological Insulator ◽  
Fermi Energy ◽  
Topological Insulators ◽  
Dirac Point ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Differential Conductance ◽  
Scanning Tunneling ◽  
Edge States ◽  
Simultaneous Observation

Gapless edge-states with a Dirac point below the Fermi energy and band-edges at the interior observed in 2D topological insulators.

Topological Insulators: Electronic Structure, Material Systems and Applications

2017 ◽  
Vol 26 (03) ◽  
pp. 1740018
Author(s):  
Parijat Sengupta
Keyword(s):  
Quantum Wells ◽  
Topological Insulator ◽  
Topological Insulators ◽  
Tight Binding ◽  
Surface States ◽  
Internal Electric Field ◽  
Linear Dispersion ◽  
Band Theory ◽  
Magnetic Perturbations ◽  
Polarized Surface

Topological insulators are a new class of materials characterized by fully spin-polarized surface states, a linear dispersion, imperviousness to external non-magnetic perturbations, and a helical character arising out of the perpendicular spin-momentum locking. This article answers in a pedagogical way the distinction between a topological and normal insulator, the role of topology in band theory of solids, and the origin of these surface states. Numerical techniques including diagonalization of the TI Hamiltonians are described to quantitatively evaluate the behaviour of topological insulator states. The Hamiltonians based on continuum and tight binding approaches are contrasted. The application of TIs as components of a fast switching environment or channel material for transistors is examined through I-V curves. The potential pitfall of such devices is presented along with techniques that could potentially circumvent the problem. Additionally, it is demonstrated that a strong internal electric field can also induce topological insulator behaviour with wurtzite nitride quantum wells as representative materials.

Layer-separable and gap-tunable topological insulators

2017 ◽  
Vol 19 (5) ◽  
pp. 3932-3936 ◽  
Author(s):  
Kai-Wei Chang ◽  
Wei Ji ◽  
Chao-Cheng Kaun
Keyword(s):  
Topological Insulator ◽  
Topological Insulators ◽  
Interlayer Coupling ◽  
Weak Interlayer

TlSe is predicted to be a layered topological insulator with rather weak interlayer coupling, and thus it can be exfoliated easily.

scholarly journals 3D Printed Polymer Photonic Topological Insulators and their Robustness to Fabrication Disorder

2022 ◽  
Author(s):  
Michael Sabatini Mattei ◽  
Boyuan Liu ◽  
Gerardo A. Mazzei Capote ◽  
Zijie Liu ◽  
Brandon G. Hacha ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Information Transfer ◽  
High Speed ◽  
Topological Insulators ◽  
Polymeric Materials ◽  
Device Fabrication ◽  
Fdtd Simulation ◽  
Design Rule ◽  
Fused Filament Fabrication ◽  
3D Printed

Photonic topological insulators have emerged as an exciting new platform for backscatter-free waveguiding even in the presence of defects, with applications in robust long-range energy and quantum information transfer, spectroscopy and sensing, chiral quantum optics, and optoelectronics. We demonstrate a design for spin-Hall photonic topological insulators with remarkably low refractive index contrast, enabling the synthesis of photonic topological waveguides from polymeric materials for the first time. Our design is compatible with additive manufacturing methods, including fused filament fabrication for microwave frequencies, and constitutes the first demonstration of a 3D printed all-dielectric photonic topological insulator. We combine rapid device fabrication through 3D printing with high-speed FDTD simulation to quantify topological protection of transmission through “omega” shaped bent topological waveguides and find that one corner in the waveguide is 3-5 times more robust to disorder than the other. This dichotomy, a new empirical design rule for ℤ2 topological insulator devices, is shown to originate in the fundamental system symmetries and is illustrated via the distributions of Poynting vectors that describe energy flow through the waveguide. Taken together, our demonstration of 3D printed polymeric spin-Hall photonic topological insulators paired with quantification of robustness to disorder at bent topological interfaces provides a rapid, flexible scheme for engineering high-performance topological photonic devices across multiple frequency regimes from microwave to THz, to visible.

Organic Rubrene/Topological Insulator Bi2Se3/SiO2 Hybrid Heterojunction Photodetector for Broadband and Ultrafast Photodetection Application

2021 ◽  
Author(s):  
Sartaj Wali ◽  
Qin Yin ◽  
Jiao Li ◽  
Guoxiang Si ◽  
Muhammad Shafi ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Topological Insulators ◽  
Optoelectronic Applications

Organic-inorganic heterostructures (OIHs) are an emerging topic that has attracted great research enthusiasm due to their unique features for electronic and optoelectronic applications. Although OIHs constructed with topological insulators and...

Topological Properties in Strained Monolayer Antimony Iodide

2021 ◽  
Vol 38 (11) ◽  
pp. 117301
Author(s):  
Danwen Yuan ◽  
Yuefang Hu ◽  
Yanmin Yang ◽  
Wei Zhang
Keyword(s):  
Topological Insulator ◽  
Topological Insulators ◽  
Energy Gap ◽  
Square Lattice ◽  
Honeycomb Lattice ◽  
Type I ◽  
Topological Properties ◽  
Dirac Semimetal ◽  
Low Dissipation ◽  
Binary Compounds

Two-dimensional (2D) topological insulators present a special phase of matter manifesting unique electronic properties. Till now, many monolayer binary compounds of Sb element, mainly with a honeycomb lattice, have been reported as 2D topological insulators. However, research of the topological insulating properties of the monolayer Sb compounds with square lattice is still lacking. Here, by means of the first-principles calculations, a monolayer SbI with square lattice is proposed to exhibit the tunable topological properties by applying strain. At different levels of the strain, the monolayer SbI shows two different structural phases: buckled square structure and buckled rectangular structure, exhibiting attracting topological properties. We find that in the buckled rectangular phase, when the strain is greater than 3.78%, the system experiences a topological phase transition from a nontrivial topological insulator to a trivial insulator, and the structure at the transition point actually is a Dirac semimetal possessing two type-I Dirac points. In addition, the system can achieve the maximum global energy gap of 72.5 meV in the topological insulator phase, implying its promising application at room temperature. This study extends the scope of 2D topological physics and provides a platform for exploring the low-dissipation quantum electronics devices.

Insect Pheromone Strategy for the Robots Coordination

2014 ◽  
Vol 613 ◽  
pp. 163-171 ◽  
Author(s):  
Jan Zelenka ◽  
Tomas Kasanický
Keyword(s):  
Cellular Automata ◽  
Shared Memory ◽  
Adaptive System ◽  
Insect Pheromone ◽  
Abstract Model ◽  
Robot Swarm ◽  
Robotic Application

Insect colony inspires scientists for years to create similar behavior in the robotic application. The main goal of our work was to develop simple and powerful algorithm which will accept dynamically changes in the size of a robot swarm due the mission. This algorithm is suitable for situations where unpredictable conditions may lead to robot fault in multi-robotics system and mission completion is endangered. In this article we would like to investigate properties of a simple pheromone based algorithm. The algorithm operates as cellular automata and partially uses an insect pheromone strategy for the robots coordination. Our abstract model is a decentralized adaptive system with a shared memory which represents the environment.

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