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.

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.

scholarly journals Orbital Edelstein effect in topological insulators

2021 ◽  
Author(s):  
Ken Osumi ◽  
Tiantian Zhang ◽  
Shuichi Murakami
Keyword(s):  
Crystal Structure ◽  
Numerical Calculation ◽  
Topological Insulator ◽  
Topological Insulators ◽  
Three Dimensional ◽  
Surface Currents ◽  
Chern Insulators ◽  
Topological Surface ◽  
Current Flows ◽  
Local Crystal Structure

Abstract We theoretically propose a gigantic orbital Edelstein effect in topological insulators and interpret the results in terms of topological surface currents. We numerically calculate the orbital Edelstein effect for a model of a three-dimensional Chern insulator as an example. Furthermore, we calculate the orbital Edelstein effect as a surface quantity using a surface Hamiltonian of a topological insulator, and numerically show that it well describes the results by direct numerical calculation. We find that the orbital Edelstein effect depends on the local crystal structure of the surface, which shows that the orbital Edelstein effect cannot be defined as a bulk quantity. We propose that Chern insulators and Z2 topological insulators can be a platform with a large orbital Edelstein effect because current flows only along the surface. We also propose candidate topological insulators for this effect. As a result, the orbital magnetization as a response to the current is much larger in topological insulators than that in metals by many orders of magnitude.

scholarly journals Glide symmetry protected higher-order topological insulators from semimetals with butterfly-like nodal lines

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Xiaoting Zhou ◽  
Chuang-Han Hsu ◽  
Cheng-Yi Huang ◽  
Mikel Iraola ◽  
Juan L. Mañes ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Topological Insulators ◽  
Surface States ◽  
Nodal Line ◽  
Higher Order ◽  
Dirac Fermion ◽  
Space Groups ◽  
Nodal Lines ◽  
Topological Semimetals ◽  
Symmetry Protected

AbstractMost topological insulators (TIs) discovered today in spinful systems can be transformed from topological semimetals (TSMs) with vanishing bulk gap via introducing the spin-orbit coupling (SOC), which manifests the intrinsic links between the gapped topological insulator phases and the gapless TSMs. Recently, we have discovered a family of TSMs in time-reversal invariant spinless systems, which host butterfly-like nodal-lines (NLs) consisting of a pair of identical concentric intersecting coplanar ellipses (CICE). In this Communication, we unveil the intrinsic link between this exotic class of nodal-line semimetals (NLSMs) and a $${{\mathbb{Z}}}_{4}$$ Z 4 = 2 topological crystalline insulator (TCI), by including substantial SOC. We demonstrate that in three space groups (i.e., Pbam (No.55), P4/mbm (No.127), and P42/mbc (No.135)), the TCI supports a fourfold Dirac fermion on the (001) surface protected by two glide symmetries, which originates from the intertwined drumhead surface states of the CICE NLs. The higher order topology is further demonstrated by the emergence of one-dimensional helical hinge states, indicating the discovery of a higher order topological insulator protected by a glide symmetry.

scholarly journals Bulk-free topological insulator Bi2Se3 nanoribbons with magnetotransport signatures of Dirac surface states

Nanoscale ◽  
2018 ◽  
Vol 10 (41) ◽  
pp. 19595-19602 ◽  
Author(s):  
Gunta Kunakova ◽  
Luca Galletti ◽  
Sophie Charpentier ◽  
Jana Andzane ◽  
Donats Erts ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Topological Insulators ◽  
Surface States ◽  
Reduced Dimensions ◽  
New Phenomena

Many applications of topological insulators (TIs) as well as new phenomena require devices with reduced dimensions.

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