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.

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 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 Discovery of a weak topological insulating state and van Hove singularity in triclinic RhBi2

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kyungchan Lee ◽  
Gunnar F. Lange ◽  
Lin-Lin Wang ◽  
Brinda Kuthanazhi ◽  
Thaís V. Trevisan ◽  
...  
Keyword(s):  
Time Reversal ◽  
Topological Insulators ◽  
Dirac Point ◽  
Saddle Points ◽  
Surface States ◽  
Van Hove Singularity ◽  
Space Group ◽  
Topological Materials ◽  
Topological Surface ◽  
Optimal Space

AbstractTime reversal symmetric (TRS) invariant topological insulators (TIs) fullfil a paradigmatic role in the field of topological materials, standing at the origin of its development. Apart from TRS protected strong TIs, it was realized early on that more confounding weak topological insulators (WTI) exist. WTIs depend on translational symmetry and exhibit topological surface states only in certain directions making it significantly more difficult to match the experimental success of strong TIs. We here report on the discovery of a WTI state in RhBi2 that belongs to the optimal space group P$$\bar{1}$$ 1 ¯ , which is the only space group where symmetry indicated eigenvalues enumerate all possible invariants due to absence of additional constraining crystalline symmetries. Our ARPES, DFT calculations, and effective model reveal topological surface states with saddle points that are located in the vicinity of a Dirac point resulting in a van Hove singularity (VHS) along the (100) direction close to the Fermi energy (EF). Due to the combination of exotic features, this material offers great potential as a material platform for novel quantum effects.

scholarly journals Many-impurity scattering on the surface of a topological insulator

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
José Luis Hernando ◽  
Yuriko Baba ◽  
Elena Díaz ◽  
Francisco Domínguez-Adame
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Topological Insulator ◽  
Disordered Systems ◽  
Spectral Properties ◽  
Random Distribution ◽  
Surface States ◽  
Impurity Scattering ◽  
Self Consistent ◽  
The Impact

AbstractWe theoretically address the impact of a random distribution of non-magnetic impurities on the electron states formed at the surface of a topological insulator. The interaction of electrons with the impurities is accounted for by a separable pseudo-potential method that allows us to obtain closed expressions for the density of states. Spectral properties of surface states are assessed by means of the Green’s function averaged over disorder realisations. For comparison purposes, the configurationally averaged Green’s function is calculated by means of two different self-consistent methods, namely the self-consistent Born approximation (SCBA) and the coherent potential approximation (CPA). The latter is often regarded as the best single-site theory for the study of the spectral properties of disordered systems. However, although a large number of works employ the SCBA for the analysis of many-impurity scattering on the surface of a topological insulator, CPA studies of the same problem are scarce in the literature. In this work, we find that the SCBA overestimates the impact of the random distribution of impurities on the spectral properties of surface states compared to the CPA predictions. The difference is more pronounced when increasing the magnitude of the disorder.

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.

scholarly journals The gigantic Rashba effect of surface states energetically buried in the topological insulator Bi2Te2Se

2014 ◽  
Vol 16 (6) ◽  
pp. 065016 ◽  
Author(s):  
K Miyamoto ◽  
T Okuda ◽  
M Nurmamat ◽  
M Nakatake ◽  
H Namatame ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Surface States ◽  
Rashba Effect ◽  
Effect Of Surface

scholarly journals Faraday Rotation Due to Surface States in the Topological Insulator (Bi1–xSbx)2Te3

Nano Letters ◽  
2017 ◽  
Vol 17 (2) ◽  
pp. 980-984 ◽  
Author(s):  
Yinming Shao ◽  
Kirk W. Post ◽  
Jhih-Sheng Wu ◽  
Siyuan Dai ◽  
Alex J. Frenzel ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Faraday Rotation ◽  
Surface States
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