scholarly journals Haldane phase on the sawtooth lattice: Edge states, entanglement spectrum, and the flat band

2017 ◽  
Vol 95 (16) ◽  
Author(s):  
Benoît Grémaud ◽  
G. George Batrouni
Keyword(s):  
Flat Band ◽  
Edge States ◽  
Entanglement Spectrum

scholarly journals Edge States in Graphene: From Gapped Flat-Band to Gapless Chiral Modes

2009 ◽  
Vol 102 (9) ◽  
Author(s):  
Wang Yao ◽  
Shengyuan A. Yang ◽  
Qian Niu
Keyword(s):  
Flat Band ◽  
Edge States

scholarly journals Tunable zero modes and quantum interferences in flat-band topological insulators

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 591
Author(s):  
Juan Zurita ◽  
Charles Creffield ◽  
Gloria Platero
Keyword(s):  
Topological Insulators ◽  
Flat Band ◽  
Topological Phase ◽  
Edge States ◽  
One Dimensional ◽  
Zero Modes ◽  
Symmetry Classes ◽  
Boundary Correspondence ◽  
High Degree ◽  
Aharonov Bohm

We investigate the interplay between Aharonov-Bohm (AB) caging and topological protection in a family of quasi-one-dimensional topological insulators, which we term CSSH ladders. Hybrids of the Creutz ladder and the SSH chain, they present a regime with completely flat bands, and a rich topological phase diagram, with several kinds of protected zero modes. These are reminiscent of the Creutz ladder edge states in some cases, and of the SSH chain edge states in others. Furthermore, their high degree of tunability, and the fact that they remain topologically protected even in small systems in the rungless case, due to AB caging, make them suitable for quantum information purposes. One of the ladders can belong to the BDI, AIII and D symmetry classes depending on its parameters, the latter being unusual in a non-superconducting model. Two of the models can also harbor topological end modes which do not follow the usual bulk-boundary correspondence, and are instead related to a Chern number. Finally, we propose some experimental setups to implement the CSSH ladders with current technology, focusing on the photonic lattice case.

scholarly journals Imaging orbital ferromagnetism in a moiré Chern insulator

Science ◽  
2021 ◽  
pp. eabd3190
Author(s):  
C. L. Tschirhart ◽  
M. Serlin ◽  
H. Polshyn ◽  
A. Shragai ◽  
Z. Xia ◽  
...  
Keyword(s):  
Quantum Interference ◽  
Chemical Potential ◽  
Hexagonal Boron Nitride ◽  
Large Change ◽  
Anomalous Hall Effect ◽  
Structural Disorder ◽  
Flat Band ◽  
Edge States ◽  
Superconducting Quantum Interference Device ◽  
Break Time

Electrons in moiré flat band systems can spontaneously break time reversal symmetry, giving rise to a quantized anomalous Hall effect. Here we use a superconducting quantum interference device to image stray magnetic fields in twisted bilayer graphene aligned to hexagonal boron nitride. We find a magnetization of several Bohr magnetons per charge carrier, demonstrating that the magnetism is primarily orbital in nature. Our measurements reveal a large change in the magnetization as the chemical potential is swept across the quantum anomalous Hall gap consistent with the expected contribution of chiral edge states to the magnetization of an orbital Chern insulator. Mapping the spatial evolution of field-driven magnetic reversal, we find a series of reproducible micron scale domains pinned to structural disorder.

scholarly journals Observation of chiral edge states in gapped nanomechanical graphene

2021 ◽  
Vol 7 (2) ◽  
pp. eabe1398
Author(s):  
Xiang Xi ◽  
Jingwen Ma ◽  
Shuai Wan ◽  
Chun-Hua Dong ◽  
Xiankai Sun
Keyword(s):  
Quantum Spin ◽  
Smooth Transition ◽  
Flat Band ◽  
Honeycomb Lattice ◽  
Edge States ◽  
Free Standing ◽  
Very High Frequency ◽  
Hall Effects ◽  
Very High ◽  
Generation Hybrid

Emerging in diverse areas of physics, edge states have been exploited as an efficient strategy of manipulating electrons, photons, and phonons for next-generation hybrid electro-optomechanical circuits. Among various edge states, gapless chiral edge states harnessing quantum spin/valley Hall effects in graphene or graphene-like materials are especially unique. Here, we report on an experimental demonstration of chiral edge states in gapped “nanomechanical graphene”—a honeycomb lattice of free-standing silicon nitride nanomechanical membranes with broken spatial inversion symmetry. These chiral edge states can emerge from the conventional flat-band edge states by tuning the on-site boundary potentials. We experimentally demonstrated that they are backscattering-immune against sharp bends and exhibit the “valley-momentum locking” effect. We further realized smooth transition between the chiral edge states and the well-known valley kink states. Our results open the door to experimental investigation of exotic graphene-related physics in the very-high-frequency integrated nanomechanical systems.

scholarly journals TOPOLOGICAL FLAT BAND MODELS AND FRACTIONAL CHERN INSULATORS

2013 ◽  
Vol 27 (24) ◽  
pp. 1330017 ◽  
Author(s):  
EMIL J. BERGHOLTZ ◽  
ZHAO LIU
Keyword(s):  
Tight Binding ◽  
Cold Atom ◽  
Flat Band ◽  
Strongly Correlated ◽  
Edge States ◽  
Fractional Quantum Hall ◽  
Flat Bands ◽  
Topological Quantum ◽  
Chern Insulators ◽  
Topological Quantum Computation

Topological insulators and their intriguing edge states can be understood in a single-particle picture and can as such be exhaustively classified. Interactions significantly complicate this picture and can lead to entirely new insulating phases, with an altogether much richer and less explored phenomenology. Most saliently, lattice generalizations of fractional quantum Hall states, dubbed fractional Chern insulators, have recently been predicted to be stabilized by interactions within nearly dispersionless bands with nonzero Chern number, C. Contrary to their continuum analogues, these states do not require an external magnetic field and may potentially persist even at room temperature, which make these systems very attractive for possible applications such as topological quantum computation. This review recapitulates the basics of tight-binding models hosting nearly flat bands with nontrivial topology, C≠0, and summarizes the present understanding of interactions and strongly correlated phases within these bands. Emphasis is made on microscopic models, highlighting the analogy with continuum Landau level physics, as well as qualitatively new, lattice specific, aspects including Berry curvature fluctuations, competing instabilities as well as novel collective states of matter emerging in bands with |C|>1. Possible experimental realizations, including oxide interfaces and cold atom implementations as well as generalizations to flat bands characterized by other topological invariants are also discussed.

Analyzing the interface trap density in SiGe capacitors using an abnormal flat band voltage shift at low temperature

2020 ◽  
Vol 13 (11) ◽  
pp. 111006
Author(s):  
Li-Chuan Sun ◽  
Chih-Yang Lin ◽  
Po-Hsun Chen ◽  
Tsung-Ming Tsai ◽  
Kuan-Ju Zhou ◽  
...  
Keyword(s):  
Low Temperature ◽  
Trap Density ◽  
Flat Band ◽  
Interface Trap Density ◽  
Interface Trap ◽  
Flat Band Voltage ◽  
Voltage Shift

scholarly journals Epitaxial Growth of Quasi-One-Dimensional Bismuth-Halide Chains with Atomically Sharp Topological Non-Trivial Edge States

ACS Nano ◽  
2021 ◽  
Author(s):  
Jincheng Zhuang ◽  
Jin Li ◽  
Yundan Liu ◽  
Dan Mu ◽  
Ming Yang ◽  
...  
Keyword(s):  
Epitaxial Growth ◽  
Edge States ◽  
One Dimensional
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