scholarly journals Multi-shaped strain soliton networks and moiré-potential-modulated band edge states in twisted bilayer SiC

RSC Advances ◽  
2021 ◽  
Vol 11 (39) ◽  
pp. 24366-24373
Author(s):  
Dawei Kang ◽  
Zheng-Wei Zuo ◽  
Zhaowu Wang ◽  
Weiwei Ju
Keyword(s):  
Twist Angle ◽  
Layered Materials ◽  
Degree Of Freedom ◽  
Band Edge ◽  
Two Dimensional ◽  
Edge States

Tuning the interlayer twist angle provides a new degree of freedom to exploit the potentially excellent properties of two dimensional layered materials.

scholarly journals Twist engineering of the two-dimensional magnetism in double bilayer chromium triiodide homostructures

2021 ◽  
Author(s):  
Hongchao Xie ◽  
Xiangpeng Luo ◽  
Gaihua Ye ◽  
Zhipeng Ye ◽  
Haiwen Ge ◽  
...  
Keyword(s):  
Twist Angle ◽  
Degree Of Freedom ◽  
Two Dimensional ◽  
Magnetic Ground State ◽  
Linear Superposition ◽  
Experimental Realization ◽  
Spin Degree ◽  
Charge Degree ◽  
Ising Magnet ◽  
Charge Degree Of Freedom

Abstract Twist engineering, or the alignment of two-dimensional (2D) crystalline layers with desired orientations, has led to tremendous success in modulating the charge degree of freedom in hetero- and homo-structures, in particular, in achieving novel correlated and topological electronic phases in moiré electronic crystals. However, although pioneering theoretical efforts have predicted nontrivial magnetism and magnons out of twisting 2D magnets, experimental realization of twist engineering spin degree of freedom remains elusive. Here, we leverage the archetypal 2D Ising magnet chromium triiodide (CrI3) to fabricate twisted double bilayer homostructures with tunable twist angles and demonstrate the successful twist engineering of 2D magnetism in them. Using linear and circular polarization-resolved Raman spectroscopy, we identify magneto-Raman signatures of a new magnetic ground state that is sharply distinct from those in natural bilayer (2L) and four-layer (4L) CrI3. With careful magnetic field and twist angle dependence, we reveal that, for a very small twist angle (~ 0.5 degree), this emergent magnetism can be well-approximated by a weighted linear superposition of those of 2L and 4L CI3 whereas, for a relatively large twist angle (~ 5 degree), it mostly resembles that of isolated 2L CrI3. Remarkably, at an intermediate twist angle (~ 1.1 degree), its magnetism cannot be simply inferred from the 2L and 4L cases, because it lacks sharp spin-flip transitions that are present in 2L and 4L CrI3 and features a dramatic Raman circular dichroism that is absent in natural 2L and 4L ones. Our results demonstrate the possibility of designing and controlling the spin degree of freedom in 2D magnets using twist engineering.

scholarly journals Excitation to defect-bound band edge states in two-dimensional semiconductors and its effect on carrier transport

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Dan Wang ◽  
Dong Han ◽  
Damien West ◽  
Nian-Ke Chen ◽  
Sheng-Yi Xie ◽  
...  
Keyword(s):  
Carrier Transport ◽  
Band Edge ◽  
Two Dimensional ◽  
Edge States

scholarly journals Anomalous properties of the band-edge states in large two-dimensional photonic quasicrystals

2007 ◽  
Vol 76 (16) ◽  
Author(s):  
Yun Lai ◽  
Zhao-Qing Zhang ◽  
Chi-Hou Chan ◽  
Leung Tsang
Keyword(s):  
Band Edge ◽  
Two Dimensional ◽  
Edge States ◽  
Photonic Quasicrystals

Experimental demonstration of directional acoustic radiation based on two-dimensional phononic crystal band edge states

2007 ◽  
Vol 90 (8) ◽  
pp. 083509 ◽  
Author(s):  
Manzhu Ke ◽  
Zhengyou Liu ◽  
Pei Pang ◽  
Chunyin Qiu ◽  
Degang Zhao ◽  
...  
Keyword(s):  
Acoustic Radiation ◽  
Phononic Crystal ◽  
Band Edge ◽  
Two Dimensional ◽  
Edge States ◽  
Experimental Demonstration

scholarly journals Twist-angle engineering of excitonic quantum interference and optical nonlinearities in stacked 2D semiconductors

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kai-Qiang Lin ◽  
Paulo E. Faria Junior ◽  
Jonas M. Bauer ◽  
Bo Peng ◽  
Bartomeu Monserrat ◽  
...  
Keyword(s):  
Quantum Interference ◽  
Second Harmonic ◽  
Electromagnetically Induced Transparency ◽  
Twist Angle ◽  
Optical Nonlinearity ◽  
Band Edge ◽  
Transition Metal Dichalcogenide ◽  
Edge States ◽  
Order Of Magnitude ◽  
Induced Transparency

AbstractTwist-engineering of the electronic structure in van-der-Waals layered materials relies predominantly on band hybridization between layers. Band-edge states in transition-metal-dichalcogenide semiconductors are localized around the metal atoms at the center of the three-atom layer and are therefore not particularly susceptible to twisting. Here, we report that high-lying excitons in bilayer WSe2 can be tuned over 235 meV by twisting, with a twist-angle susceptibility of 8.1 meV/°, an order of magnitude larger than that of the band-edge A-exciton. This tunability arises because the electronic states associated with upper conduction bands delocalize into the chalcogenide atoms. The effect gives control over excitonic quantum interference, revealed in selective activation and deactivation of electromagnetically induced transparency (EIT) in second-harmonic generation. Such a degree of freedom does not exist in conventional dilute atomic-gas systems, where EIT was originally established, and allows us to shape the frequency dependence, i.e., the dispersion, of the optical nonlinearity.

A design rule for two-dimensional van der Waals heterostructures with unconventional band alignments

2020 ◽  
Vol 22 (5) ◽  
pp. 3037-3047 ◽  
Author(s):  
Yuan Si ◽  
Hong-Yu Wu ◽  
Ji-Chun Lian ◽  
Wei-Qing Huang ◽  
Wang-Yu Hu ◽  
...  
Keyword(s):  
Van Der Waals ◽  
Interlayer Coupling ◽  
Band Alignment ◽  
Band Edge ◽  
Design Rule ◽  
Two Dimensional ◽  
Edge States ◽  
Van Der Waals Heterostructures ◽  
Band Alignments

A feasible rule to design unconventional band alignment by inducing the hybridization of band-edge states via interlayer coupling.

scholarly journals Group Velocity Modulation and Light Field Focusing of the Edge States in Chirped Valley Graphene Plasmonic Metamaterials

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1808
Author(s):  
Liqiang Zhuo ◽  
Huiru He ◽  
Ruimin Huang ◽  
Shaojian Su ◽  
Zhili Lin ◽  
...  
Keyword(s):  
Group Velocity ◽  
Light Field ◽  
Slow Light ◽  
Dielectric Materials ◽  
Degree Of Freedom ◽  
Geometrical Parameters ◽  
Edge States ◽  
Velocity Modulation ◽  
Plasmonic Metamaterials ◽  
On Chip

The valley degree of freedom, like the spin degree of freedom in spintronics, is regarded as a new information carrier, promoting the emerging valley photonics. Although there exist topologically protected valley edge states which are immune to optical backscattering caused by defects and sharp edges at the inverse valley Hall phase interfaces composed of ordinary optical dielectric materials, the dispersion and the frequency range of the edge states cannot be tuned once the geometrical parameters of the materials are determined. In this paper, we propose a chirped valley graphene plasmonic metamaterial waveguide composed of the valley graphene plasmonic metamaterials (VGPMs) with regularly varying chemical potentials while keeping the geometrical parameters constant. Due to the excellent tunability of graphene, the proposed waveguide supports group velocity modulation and zero group velocity of the edge states, where the light field of different frequencies focuses at different specific locations. The proposed structures may find significant applications in the fields of slow light, micro–nano-optics, topological plasmonics, and on-chip light manipulation.

Theoretical realization of two-dimensional Dirac/Weyl line-node and traversing edge states in penta-X2Y monolayers

2021 ◽  
Vol 23 ◽  
pp. 101057
Author(s):  
Lirong Wang ◽  
Lei Jin ◽  
Guodong Liu ◽  
Ying Liu ◽  
Xuefang Dai ◽  
...  
Keyword(s):  
Two Dimensional ◽  
Edge States ◽  
Line Node

scholarly journals Topological gaps by twisting

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Matheus I. N. Rosa ◽  
Massimo Ruzzene ◽  
Emil Prodan
Keyword(s):  
Magnetic Field ◽  
Quantum Hall Effect ◽  
Twist Angle ◽  
Quantum Hall ◽  
Topological Phases ◽  
Edge States ◽  
Layered Systems ◽  
Virtual Laboratories ◽  
Higher Dimensional ◽  
Chern Numbers

AbstractTwisted bilayered systems such as bilayered graphene exhibit remarkable properties such as superconductivity at magic angles and topological insulating phases. For generic twist angles, the bilayers are truly quasiperiodic, a fact that is often overlooked and that has consequences which are largely unexplored. Herein, we uncover that twisted n-layers host intrinsic higher dimensional topological phases, and that those characterized by second Chern numbers can be found in twisted bi-layers. We employ phononic lattices with interactions modulated by a second twisted lattice and reveal Hofstadter-like spectral butterflies in terms of the twist angle, which acts as a pseudo magnetic field. The phason provided by the sliding of the layers lives on 2n-tori and can be used to access and manipulate the edge states. Our work demonstrates how multi-layered systems are virtual laboratories for studying the physics of higher dimensional quantum Hall effect, and can be employed to engineer topological pumps via simple twisting and sliding.

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