scholarly journals Symmetry-protected solitons and bulk-boundary correspondence in generalized Jackiw–Rebbi models

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chang-geun Oh ◽  
Sang-Hoon Han ◽  
Sangmo Cheon
Keyword(s):  
Internal Field ◽  
Fermion Field ◽  
Edge States ◽  
Global Minima ◽  
Rotation Symmetry ◽  
Fermion Fields ◽  
Boundary Correspondence ◽  
Symmetry Protected ◽  
Chiral Solitons

AbstractWe investigate the roles of symmetry and bulk-boundary correspondence in characterizing topological edge states in generalized Jackiw–Rebbi (JR) models. We show that time-reversal (T), charge-conjugation (C), parity (P), and discrete internal field rotation ($$Z_n$$ Z n ) symmetries protect and characterize the various types of edge states such as chiral and nonchiral solitons via bulk-boundary correspondence in the presence of the multiple vacua. As two representative models, we consider the JR model composed of a single fermion field having a complex mass and the generalized JR model with two massless but interacting fermion fields. The JR model shows nonchiral solitons with the $$Z_2$$ Z 2 rotation symmetry, whereas it shows chiral solitons with the broken $$Z_2$$ Z 2 rotation symmetry. In the generalized JR model, only nonchiral solitons can emerge with only $$Z_2$$ Z 2 rotation symmetry, whereas both chiral and nonchiral solitons can exist with enhanced $$Z_4$$ Z 4 rotation symmetry. Moreover, we find that the nonchiral solitons have C, P symmetries while the chiral solitons do not, which can be explained by the symmetry-invariant lines connecting degenerate vacua. Finally, we find the symmetry correspondence between multiply-degenerate global vacua and solitons such that T, C, P symmetries of a soliton inherit from global minima that are connected by the soliton, which provides a novel tool for the characterization of topological solitons.

scholarly journals Defective edge states and anomalous bulk-boundary correspondence for topological insulators under non-Hermitian similarity transformation

2020 ◽  
Vol 34 (09) ◽  
pp. 2050146
Author(s):  
C. Wang ◽  
X.-R. Wang ◽  
C.-X. Guo ◽  
S.-P. Kou
Keyword(s):  
Chiral Symmetry ◽  
Topological Insulators ◽  
Skin Effect ◽  
Similarity Transformation ◽  
Topological Invariant ◽  
Inversion Symmetry ◽  
Edge States ◽  
Boundary Correspondence ◽  
Zhang Model ◽  
Symmetry Protected

It was known that for non-Hermitian topological systems due to the non-Hermitian skin effect, the bulk-edge correspondence is broken down. In this paper, by using one-dimensional Su–Schrieffer–Heeger model and two-dimensional (deformed) Qi–Wu–Zhang model as examples, the focus is on a special type of non-Hermitian topological system without non-Hermitian skin effect — topological systems under non-Hermitian similarity transformation. In these non-Hermitian systems, the defective edge states and the breakdown of bulk-edge correspondence are discovered. To characterize the topological properties, a new type of inversion symmetry-protected topological invariant — total [Formula: see text] topological invariant — has been introduced. In topological phases, defective edge states appear. With the help of the effective edge Hamiltonian, it was found that the defective edge states are protected by (generalized) chiral symmetry and thus the (singular) defective edge states are unstable against the perturbation breaking the chiral symmetry. In addition, the results are generalized to non-Hermitian topological insulators with inversion symmetry in higher dimensions. This work could help people to understand the defective edge states and the breakdown of bulk-edge correspondence for non-Hermitian topological systems.

scholarly journals Direct quantification of topological protection in symmetry-protected photonic edge states at telecom wavelengths

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Sonakshi Arora ◽  
Thomas Bauer ◽  
René Barczyk ◽  
Ewold Verhagen ◽  
L. Kuipers
Keyword(s):  
Near Field ◽  
Edge States ◽  
Quantum Networks ◽  
Hall Effects ◽  
Upper Limits ◽  
On Chip ◽  
Symmetry Protected ◽  
Topological Robustness ◽  
Direct Quantification ◽  
Sub Wavelength

AbstractTopological on-chip photonics based on tailored photonic crystals (PhCs) that emulate quantum valley-Hall effects has recently gained widespread interest owing to its promise of robust unidirectional transport of classical and quantum information. We present a direct quantitative evaluation of topological photonic edge eigenstates and their transport properties in the telecom wavelength range using phase-resolved near-field optical microscopy. Experimentally visualizing the detailed sub-wavelength structure of these modes propagating along the interface between two topologically non-trivial mirror-symmetric lattices allows us to map their dispersion relation and differentiate between the contributions of several higher-order Bloch harmonics. Selective probing of forward- and backward-propagating modes as defined by their phase velocities enables direct quantification of topological robustness. Studying near-field propagation in controlled defects allows us to extract upper limits of topological protection in on-chip photonic systems in comparison with conventional PhC waveguides. We find that protected edge states are two orders of magnitude more robust than modes of conventional PhC waveguides. This direct experimental quantification of topological robustness comprises a crucial step toward the application of topologically protected guiding in integrated photonics, allowing for unprecedented error-free photonic quantum networks.

Topological photonic crystals in the visible: design and angle-resolved characterization of the bulk and edge states

2018 ◽  
Author(s):  
Siying Peng ◽  
Nick Schilder ◽  
Xiang Ni ◽  
Sophie Meuret ◽  
Hugo Doeleman ◽  
...  
Keyword(s):  
Photonic Crystals ◽  
Edge States

scholarly journals The (2+1) dimensional metric f (R) gravity non-minimally coupled with fermion field

2021 ◽  
Vol 2090 (1) ◽  
pp. 012065
Author(s):  
Nurgissa Myrzakulov ◽  
Gulnur Tursumbayeva ◽  
Shamshyrak Myrzakulova
Keyword(s):  
Gravitational Theory ◽  
Noether Symmetry ◽  
Fermion Field ◽  
Field Equations ◽  
Friedmann Equations ◽  
Fermion Fields ◽  
Cosmological Solutions

Abstract In this article, we examine a gravitational theory including a fermion field that is non-minimally coupled to metric f (R) gravity in (2+1) dimensions. We give the field equations for fermion fields and Friedmann equations. In this context, we study cosmological solutions of the field equations using these forms obtained by the existent of Noether symmetry.

scholarly journals Direct quantification of topological protection in symmetry-protected photonic edge states at telecom wavelengths

2021 ◽  
Author(s):  
Sonakshi Arora ◽  
Thomas Bauer ◽  
René Barczyk ◽  
Ewold Verhagen ◽  
Kobus Kuipers
Keyword(s):  
Edge States ◽  
Symmetry Protected ◽  
Direct Quantification

scholarly journals A PATH-INTEGRAL APPROACH FOR BOSONIC EFFECTIVE THEORIES FOR FERMION FIELDS IN FOUR AND THREE DIMENSIONS

2000 ◽  
Vol 15 (05) ◽  
pp. 755-770 ◽  
Author(s):  
LUIZ C. L. BOTELHO
Keyword(s):  
Path Integral ◽  
Infrared Region ◽  
Three Dimensions ◽  
Integral Approach ◽  
Ultraviolet Region ◽  
Fermion Field ◽  
Massive Fermion ◽  
Bosonic Field ◽  
Fermion Fields ◽  
Effective Theories

We study four-dimensional effective bosonic field theories for (A) massive fermion field in the infrared region and (B) massive fermion in the ultraviolet region by using an appropriate fermion path integral chiral variable change and (C) Polyakov's Fermi–Bose transmutation in the 3D-Abelian Thirring model and its triviality as a quantum field theory.

scholarly journals Some Aspects of Supersymmetric Field Theories with Minimal Length and Maximal Momentum

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Kourosh Nozari ◽  
F. Moafi ◽  
F. Rezaee Balef
Keyword(s):  
Deformation Parameter ◽  
Heisenberg Algebra ◽  
Minimal Length ◽  
Field Theories ◽  
Majorana Fermion ◽  
Fermion Field ◽  
Free Fermion ◽  
Supersymmetric Field Theories ◽  
Fermion Fields ◽  
Maximal Momentum

We consider a real scalar field and a Majorana fermion field to construct a supersymmetric quantum theory of free fermion fields based on the deformed Heisenberg algebra[x,p] = iℏ(1−βp+2β2p2), whereβis a deformation parameter. We present a deformed supersymmetric algebra in the presence of minimal length and maximal momentum.

scholarly journals Photonic topological insulator with broken time-reversal symmetry

2016 ◽  
Vol 113 (18) ◽  
pp. 4924-4928 ◽  
Author(s):  
Cheng He ◽  
Xiao-Chen Sun ◽  
Xiao-Ping Liu ◽  
Ming-Hui Lu ◽  
Yulin Chen ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Time Reversal ◽  
Magnetoelectric Coupling ◽  
Electronic Systems ◽  
Time Reversal Symmetry ◽  
Edge States ◽  
Protection Mechanism ◽  
Fundamental Particles ◽  
Left And Right ◽  
Symmetry Protected

A topological insulator is a material with an insulating interior but time-reversal symmetry-protected conducting edge states. Since its prediction and discovery almost a decade ago, such a symmetry-protected topological phase has been explored beyond electronic systems in the realm of photonics. Electrons are spin-1/2 particles, whereas photons are spin-1 particles. The distinct spin difference between these two kinds of particles means that their corresponding symmetry is fundamentally different. It is well understood that an electronic topological insulator is protected by the electron’s spin-1/2 (fermionic) time-reversal symmetry Tf2=−1. However, the same protection does not exist under normal circumstances for a photonic topological insulator, due to photon’s spin-1 (bosonic) time-reversal symmetry Tb2=1. In this work, we report a design of photonic topological insulator using the Tellegen magnetoelectric coupling as the photonic pseudospin orbit interaction for left and right circularly polarized helical spin states. The Tellegen magnetoelectric coupling breaks bosonic time-reversal symmetry but instead gives rise to a conserved artificial fermionic-like-pseudo time-reversal symmetry, Tp (Tp2=−1), due to the electromagnetic duality. Surprisingly, we find that, in this system, the helical edge states are, in fact, protected by this fermionic-like pseudo time-reversal symmetry Tp rather than by the bosonic time-reversal symmetry Tb. This remarkable finding is expected to pave a new path to understanding the symmetry protection mechanism for topological phases of other fundamental particles and to searching for novel implementations for topological insulators.

scholarly journals Non-Hermitian Skin Effect in a Non-Hermitian Electrical Circuit

Research ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Shuo Liu ◽  
Ruiwen Shao ◽  
Shaojie Ma ◽  
Lei Zhang ◽  
Oubo You ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Periodic Boundary Condition ◽  
Periodic Boundary ◽  
Skin Effect ◽  
Open Circuit ◽  
Electrical Circuit ◽  
Finite System ◽  
Open Boundary ◽  
Edge States ◽  
Boundary Correspondence

The conventional bulk-boundary correspondence directly connects the number of topological edge states in a finite system with the topological invariant in the bulk band structure with periodic boundary condition (PBC). However, recent studies show that this principle fails in certain non-Hermitian systems with broken reciprocity, which stems from the non-Hermitian skin effect (NHSE) in the finite system where most of the eigenstates decay exponentially from the system boundary. In this work, we experimentally demonstrate a 1D non-Hermitian topological circuit with broken reciprocity by utilizing the unidirectional coupling feature of the voltage follower module. The topological edge state is observed at the boundary of an open circuit through an impedance spectra measurement between adjacent circuit nodes. We confirm the inapplicability of the conventional bulk-boundary correspondence by comparing the circuit Laplacian between the periodic boundary condition (PBC) and open boundary condition (OBC). Instead, a recently proposed non-Bloch bulk-boundary condition based on a non-Bloch winding number faithfully predicts the number of topological edge states.

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