scholarly journals Edge states and the valley Hall effect

2020 ◽  
Vol 368 ◽  
pp. 107142 ◽  
Author(s):  
A. Drouot ◽  
M.I. Weinstein
Keyword(s):  
Hall Effect ◽  
Edge States ◽  
Valley Hall Effect

scholarly journals Quantum spin-valley Hall effect in AB-stacked bilayer silicene

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Kyu Won Lee ◽  
Cheol Eui Lee
Keyword(s):  
Hall Effect ◽  
Density Functional ◽  
Tight Binding ◽  
Quantum Spin ◽  
Chern Number ◽  
Antiferromagnetic Order ◽  
Gradual Change ◽  
Edge States ◽  
Binding Model ◽  
Valley Hall Effect

AbstractOur density functional theory calculations show that while AB-stacked bilayer silicene has a non-quantized spin-valley Chern number, there exist backscattering-free gapless edge states within the bulk gap, leading to a quantum spin-valley Hall effect. Using a tight-binding model for a honeycomb bilayer, we found that the interlayer potential difference and the staggered AB-sublattice potential lead to abrupt and gradual change of the valley Chern number from a quantized value to zero, respectively, while maintaining backscattering-free gapless edge states if the valley Chern number is not too close to zero. Under an inversion symmetry-breaking potential in the form of the staggered AB-sublattice potential, such as an antiferromagnetic order and a hexagonal diatomic sheet, a finite but non-quantized (spin-)valley Chern number can correspond to a quantum (spin-)valley Hall insulator.

scholarly journals Enabling novel dispersion and topological characteristics in mechanical lattices via stable negative inertial coupling

2021 ◽  
Vol 477 (2252) ◽  
pp. 20200820
Author(s):  
H. Al Ba’ba’a ◽  
X. Zhu ◽  
Q. Wang
Keyword(s):  
Hall Effect ◽  
Topological Insulators ◽  
Periodic Structures ◽  
Edge States ◽  
New Developments ◽  
Inertial Coupling ◽  
Mechanical Analogue ◽  
Topological Characteristics ◽  
Elastically Supported ◽  
Valley Hall Effect

Mechanical topological insulators have enabled a myriad of unprecedented characteristics that are otherwise not conceivable in traditional periodic structures. While rich in dynamics, new developments in the domain of mechanical topological systems are hindered by their inherent inability to exhibit negative elastic or inertial couplings owing to the inevitable loss of dynamical stability. The aim of this paper is, therefore, to remedy this challenge by introducing a class of architected inertial metamaterials (AIMs) as a platform for designing mechanical lattices with novel topological and dispersion traits. We show that carefully coupling elastically supported masses via moment-free rigid linkages invokes a dynamically stable negative inertial coupling, which is essential for topological classes in need of such negative interconnection. The potential of the proposed AIMs is demonstrated via three examples: (i) a mechanical analogue of Majorana edge states, (ii) a square diatomic AIM that can sustain the quantum valley Hall effect (classically arising in hexagonal lattices), and (iii) a square tetratomic AIM with topological corner modes. We envision that the presented framework will pave the way for a plethora of robust topological mechanical systems.

scholarly journals Ultrafast non-excitonic valley Hall effect in MoS2/WTe2 heterobilayers

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jekwan Lee ◽  
Wonhyeok Heo ◽  
Myungjun Cha ◽  
Kenji Watanabe ◽  
Takashi Taniguchi ◽  
...  
Keyword(s):  
Hall Effect ◽  
Quantitative Information ◽  
Exciton Energy ◽  
Electron Hole ◽  
Kerr Rotation ◽  
Polarized Electrons ◽  
Spatially Resolved ◽  
Long Valley ◽  
Bound Electron ◽  
Valley Hall Effect

AbstractThe valley Hall effect (VHE) in two-dimensional (2D) van der Waals (vdW) crystals is a promising approach to study the valley pseudospin. Most experiments so far have used bound electron-hole pairs (excitons) through local photoexcitation. However, the valley depolarization of such excitons is fast, so that several challenges remain to be resolved. We address this issue by exploiting a unipolar VHE using a heterobilayer made of monolayer MoS2/WTe2 to exhibit a long valley-polarized lifetime due to the absence of electron-hole exchange interaction. The unipolar VHE is manifested by reduced photoluminescence at the MoS2 A exciton energy. Furthermore, we provide quantitative information on the time-dependent valley Hall dynamics by performing the spatially-resolved ultrafast Kerr-rotation microscopy; we find that the valley-polarized electrons persist for more than 4 nanoseconds and the valley Hall mobility exceeds 4.49 × 103 cm2/Vs, which is orders of magnitude larger than previous reports.

Magnetocapacitance Investigation of Quantum Hall Effect and Edge States

1997 ◽  
Vol 11 (22) ◽  
pp. 2593-2619 ◽  
Author(s):  
Sadao Takaoka ◽  
Kenichi Oto ◽  
Kazuo Murase
Keyword(s):  
Hall Effect ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
Electron System ◽  
Edge Length ◽  
Capacitance Measurement ◽  
Edge States ◽  
Bulk Conductivity ◽  
Cyclotron Radius ◽  
Bulk State

The quantum Hall effect for the GaAs/AlGaAs heterostrcture is investigated by an ac capacitance measurement between the two-dimensional electron system (2DES) and the gate on GaAs/AlGaAs. The capacitance minima at the quantum Hall plateaus are mainly determined not by the 2DES area under the gate but by the edge length of 2DES. There exists the high conductive region due to the edge states along the 2DES boundary, when the bulk conductivity σxx is small enough at low temperatures and high magnetic fields. From the temperature and frequency dependence of the capacitance minima, it is found that the measured capacitance consists of the contribution from the edge states and that of the bulk state, which is treated as a distributed circuit of a resistive plate with the conductivity σxx. The evaluated width of edge states from the capacitance is much larger than the magnetic length and the cyclotron radius expected from the one-electron picture. This wide width of edge states can be explained by the compressible-incompressible strip model, in which the screening effect is taken into account. Further the bulk conductivity of less than 10-12 S (S=1/Ω) is measured by the capacitance of the Corbino geometry sample, where the edge states are absent and the capacitance is determined by only σxx in this geometry. The localization of the bulk state is investigated by the obtained σxx.

VERTEX OPERATORS IN THE QUANTUM HALL EFFECT

1991 ◽  
Vol 05 (03) ◽  
pp. 509-527 ◽  
Author(s):  
MICHAEL STONE
Keyword(s):  
Hall Effect ◽  
Landau Level ◽  
Quantum Hall Effect ◽  
Group Action ◽  
Quantum Hall ◽  
Vertex Operators ◽  
Edge States ◽  
Many Body ◽  
Level I ◽  
The Many

The edge states of the quantum Hall effect carry representations of chiral current algebras and their associated groups. In the simplest case of a single filled Landau level, I demonstrate explicitly how the group action affects the many-body states, and why the Kac-Peterson cocycle appears in the group multiplication law. I show how these representations may be used to construct vertex operators which create localised edge excitations, and indicate how they are related to the bulk quasi-particles.

scholarly journals Microscopic Origin of the Valley Hall Effect in Transition Metal Dichalcogenides Revealed by Wavelength-Dependent Mapping

Nano Letters ◽  
2017 ◽  
Vol 17 (9) ◽  
pp. 5719-5725 ◽  
Author(s):  
Nicolas Ubrig ◽  
Sanghyun Jo ◽  
Marc Philippi ◽  
Davide Costanzo ◽  
Helmuth Berger ◽  
...  
Keyword(s):  
Transition Metal ◽  
Hall Effect ◽  
Transition Metal Dichalcogenides ◽  
Metal Dichalcogenides ◽  
Valley Hall Effect ◽  
Microscopic Origin
Sign in / Sign up

Export Citation Format

Share Document