scholarly journals Distinction between electron states formed at topological insulator interfaces with the trivial phase and vacuum

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. S. Kazakov ◽  
A. V. Galeeva ◽  
A. I. Artamkin ◽  
A. V. Ikonnikov ◽  
L. I. Ryabova ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Topological Insulators ◽  
Topological Phase ◽  
Electron States ◽  
Cap Layer

AbstractIn this paper, we show that electron states formed in topological insulators at the interfaces topological phase–trivial phase and topological phase–vacuum may possess different properties. This is demonstrated on an example of heterostructures based on thick topological Hg1−xCdxTe films, in which the PT-symmetric terahertz photoconductivity is observed. It is shown that the effect originates from features of the interface topological film–trivial buffer/cap layer. The PT-symmetric terahertz photoconductivity is not provided by electron states formed at the interface topological film–vacuum.

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 Experimental Observation of Temperature-Driven Topological Phase Transition in HgTe/CdHgTe Quantum Wells

2019 ◽  
Author(s):  
Maksim Zholudev ◽  
Aleksandr Kadykov ◽  
Mikhail Fadeev ◽  
Michal Marcinkiewicz ◽  
Sandra Ruffenach ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Quantum Wells ◽  
Topological Insulator ◽  
Critical Magnetic Field ◽  
Topological Phase ◽  
Temperature Dependent ◽  
Transition Parameter ◽  
Topological Phase Transition ◽  
Band Insulator

We report on comparison between temperature-dependent magneto¬absorption and magnetotransport spectroscopy of HgTe/CdHgTe quantum wells in terms of detection of phase transition between topological insulator and band insulator states. Our results demonstrate that temperature-dependent magnetospectroscopy is a powerful tool to discriminate trivial and topological insulator phases, yet magnetotransport method is shown to have advantages for clear manifestation of the phase transition with accurate quantitative values of transition parameter (i.e. critical magnetic field Bc).

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.

Exotic Topological Insulator States and Topological Phase Transitions in Sb2Se3–Bi2Se3 Heterostructures

ACS Nano ◽  
2012 ◽  
Vol 6 (3) ◽  
pp. 2345-2352 ◽  
Author(s):  
Qianfan Zhang ◽  
Zhiyong Zhang ◽  
Zhiyong Zhu ◽  
Udo Schwingenschlögl ◽  
Yi Cui
Keyword(s):  
Phase Transitions ◽  
Topological Insulator ◽  
Topological Phase ◽  
Topological Phase Transitions

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.

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