Two-dimensional ferroelastic topological insulator with tunable topological edge states in single-layer ZrAsX (X = Br and Cl)

2019 ◽  
Vol 7 (31) ◽  
pp. 9743-9747 ◽  
Author(s):  
Xiangting Hu ◽  
Ning Mao ◽  
Hao Wang ◽  
Chengwang Niu ◽  
Baibiao Huang ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Single Layer ◽  
Two Dimensional ◽  
Edge States

Here we predict theoretically that topological edge states can be significantly tuned by switching the ferroelastic ordering in a two-dimensional (2D) topological insulator.

scholarly journals Dynamic impurities in two-dimensional topological-insulator edge states

2021 ◽  
Vol 104 (20) ◽  
Author(s):  
Simon Wozny ◽  
Martin Leijnse ◽  
Sigurdur I. Erlingsson
Keyword(s):  
Topological Insulator ◽  
Two Dimensional ◽  
Edge States

scholarly journals Twisted bulk-boundary correspondence of fragile topology

Science ◽  
2020 ◽  
Vol 367 (6479) ◽  
pp. 794-797 ◽  
Author(s):  
Zhi-Da Song ◽  
Luis Elcoro ◽  
B. Andrei Bernevig
Keyword(s):  
Boundary Conditions ◽  
Topological Insulator ◽  
Experimental Verification ◽  
Real Space ◽  
Two Dimensional ◽  
Edge States ◽  
Quantum Numbers ◽  
Boundary Correspondence ◽  
Topological States ◽  
Twisted Boundary Conditions

A topological insulator reveals its nontrivial bulk through the presence of gapless edge states: This is called the bulk-boundary correspondence. However, the recent discovery of “fragile” topological states with no gapless edges casts doubt on this concept. We propose a generalization of the bulk-boundary correspondence: a transformation under which the gap between the fragile phase and other bands must close. We derive specific twisted boundary conditions (TBCs) that can detect all the two-dimensional eigenvalue fragile phases. We develop the concept of real-space invariants, local good quantum numbers in real space, which fully characterize these phases and determine the number of gap closings under the TBCs. Realizations of the TBCs in metamaterials are proposed, thereby providing a route to their experimental verification.

Ferromagnetic dual topological insulator in a two-dimensional honeycomb lattice

2020 ◽  
Vol 7 (9) ◽  
pp. 2431-2438
Author(s):  
Hao Wang ◽  
Ning Mao ◽  
Chengwang Niu ◽  
Shiying Shen ◽  
Myung-Hwan Whangbo ◽  
...  
Keyword(s):  
Hall Effect ◽  
Topological Insulator ◽  
Topological Insulators ◽  
Anomalous Hall Effect ◽  
Topological Invariant ◽  
Honeycomb Lattice ◽  
Two Dimensional ◽  
Edge States ◽  
Quantum Anomalous Hall Effect ◽  
Significant Attention

Magnetic topological insulators (TIs), including the quantum anomalous Hall effect and antiferromagnetic TIs, have attracted significant attention owing to the exotic properties they give rise to, however, ferromagnetic TIs with gapless surface/edge states and a nonzero topological invariant have not been reported so far.

scholarly journals Imaging quantum spin Hall edges in monolayer WTe2

2019 ◽  
Vol 5 (2) ◽  
pp. eaat8799 ◽  
Author(s):  
Yanmeng Shi ◽  
Joshua Kahn ◽  
Ben Niu ◽  
Zaiyao Fei ◽  
Bosong Sun ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Topological Insulator ◽  
Gate Voltage ◽  
Quantum Spin ◽  
Two Dimensional ◽  
Edge States ◽  
Local Conductivity ◽  
Quantum Spin Hall

A two-dimensional (2D) topological insulator exhibits the quantum spin Hall (QSH) effect, in which topologically protected conducting channels exist at the sample edges. Experimental signatures of the QSH effect have recently been reported in an atomically thin material, monolayer WTe2. Here, we directly image the local conductivity of monolayer WTe2 using microwave impedance microscopy, establishing beyond doubt that conduction is indeed strongly localized to the physical edges at temperatures up to 77 K and above. The edge conductivity shows no gap as a function of gate voltage, and is suppressed by magnetic field as expected. We observe additional conducting features which can be explained by edge states following boundaries between topologically trivial and nontrivial regions. These observations will be critical for interpreting and improving the properties of devices incorporating WTe2. Meanwhile, they reveal the robustness of the QSH channels and the potential to engineer them in the monolayer material platform.

A two-dimensional robust topological insulator with coexisting ferroelectric and valley polarization

2019 ◽  
Vol 7 (30) ◽  
pp. 9406-9412 ◽  
Author(s):  
Xing-kai Hu ◽  
Zhao-xia Pang ◽  
Chang-wen Zhang ◽  
Pei-ji Wang ◽  
Ping Li ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Two Dimensional ◽  
Edge States ◽  
Valley Polarization

The coexistence of ferroelectric and valley polarization, as well as topological edge states, are found in fluorinated methyl-functionalized bismuthene films.

scholarly journals Quasistationary states in a quantum dot formed at the edge of a topological insulator by magnetic barriers with finite transparency

2021 ◽  
Vol 2103 (1) ◽  
pp. 012201
Author(s):  
D V Khomitsky ◽  
E A Lavrukhina
Keyword(s):  
Topological Insulator ◽  
Two Dimensional ◽  
Edge States ◽  
Stationary Schrödinger Equation ◽  
Double Barrier ◽  
One Dimensional ◽  
Occupation Numbers ◽  
The One ◽  
Magnetic Barriers ◽  
Double Barrier Structure

Abstract A model of quasistationary states is constructed for the one-dimensional edge states propagating along the edge of a two-dimensional topological insulator based on HgTe/CdTe quantum well in the presence of magnetic barriers with finite transparency. The lifetimes of these quasistationary states are found analytically and numerically via different approaches including the solution of the stationary Schrödinger equation with complex energy and the solution of the transmission problem for a double barrier structure. The results can serve as a guide for determining the parameters of magnetic barriers creating the quantum dots where the lifetimes for the broadened discrete levels are long enough for manipulation with their occupation numbers by external fields.

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