scholarly journals Observation of chiral zero mode in inhomogeneous three-dimensional Weyl metamaterials

Science ◽  
2019 ◽  
Vol 363 (6423) ◽  
pp. 148-151 ◽  
Author(s):  
Hongwei Jia ◽  
Ruixing Zhang ◽  
Wenlong Gao ◽  
Qinghua Guo ◽  
Biao Yang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Gauge Field ◽  
Zero Mode ◽  
Three Dimensional ◽  
Chiral Anomaly ◽  
Zero Modes ◽  
Individual Unit ◽  
Unit Cells ◽  
Device Applications ◽  
The Individual

Owing to the chirality of Weyl nodes, the Weyl systems can support one-way chiral zero modes under a strong magnetic field, which leads to nonconservation of chiral currents—the so-called chiral anomaly. Although promising for robust transport of optical information, the zero chiral bulk modes have not been observed in photonics. Here we design an inhomogeneous Weyl metamaterial in which a gauge field is generated for the Weyl nodes by engineering the individual unit cells. We experimentally confirm the presence of the gauge field and observe the zero-order chiral Landau level with one-way propagation. Without breaking the time-reversal symmetry, our system provides a route for designing an artificial magnetic field in three-dimensional photonic Weyl systems and may have potential for device applications in photonics.

CHIRAL ANOMALY IN EUCLIDEAN (2+1)-DIMENSIONAL SPACE AND AN APPLICATION TO THE QUANTUM HALL EFFECT

2008 ◽  
Vol 22 (17) ◽  
pp. 2675-2689 ◽  
Author(s):  
PAUL BRACKEN
Keyword(s):  
Magnetic Field ◽  
Dirac Equation ◽  
Hall Effect ◽  
Quantum Hall Effect ◽  
Zero Mode ◽  
Dimensional Space ◽  
Quantum Hall ◽  
Chiral Anomaly ◽  
Regularization Procedure ◽  
Chiral Transformation

The chiral anomaly in (2+1)-dimensions and its relationship to the zero mode of the Dirac equation in the massless case is studied. Solutions are obtained for the Dirac equation under a vector potential which generates a constant magnetic field. It is shown that there is an anomaly term associated with the corresponding chiral transformation. It can be calculated by using the regularization procedure of Fujikawa. The results are applied to the quantum Hall effect.

scholarly journals Weyl-triplons in SrCu2(BO3)2

2020 ◽  
Author(s):  
Pinaki Sengupta ◽  
DHIMAN BHOWMICK
Keyword(s):  
Magnetic Field ◽  
Longitudinal Magnetic Field ◽  
Inelastic Neutron Scattering ◽  
Three Dimensional ◽  
Inelastic Neutron ◽  
Nodal Line ◽  
Low Energy ◽  
Zero Field ◽  
Quantum Magnet ◽  
The Individual

Abstract Presence of Weyl node, nodal line or nodal surface in the band structure is a signature of topological gapless phase in a three-dimensional(3D) material. Here, we propose that Weyl triplons are expected to appear in the low energy magnetic excitations in the canonical Shastry-Sutherland compound, \ce{SrCu2(BO3)2}, a quasi-2D quantum magnet. Our results show that whena minimal, realistic inter-layer coupling is added to the well-established microscopicmodel describing the excitation spectrum of the individual layers,the Dirac points that appears in the zero-field triplon spectrum of the 2D modelsplits into two pairs of Weyl points along the Kz direction. Varying the strength of the inter-layer Dzyaloshinskii–Moriya(DM) interaction and applying asmall longitudinal magnetic field results in a range of band topologytransitions accompanied by changing numbers of Weyl points. We propose inelastic neutron scattering along with thermal Hall effect as the experimental techniques to detect the presence of Weyl-node in the triplon spectrum of this material.

scholarly journals Observation of magnetic adatom-induced Majorana vortex and its fusion with field-induced Majorana vortex in an iron-based superconductor

2020 ◽  
Author(s):  
Peng Fan ◽  
Fazhi Yang ◽  
Guojian Qian ◽  
Hui Chen ◽  
Yu-Yang Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Bound States ◽  
Zero Mode ◽  
Fault Tolerant ◽  
Abrikosov Vortex ◽  
Zero Modes ◽  
Topological Quantum ◽  
Iron Based ◽  
Dual Origin ◽  
Single Material

Abstract Braiding Majorana zero modes is essential for fault-tolerant topological quantum computing. Iron-based superconductors with nontrivial band topology have recently emerged as a surprisingly promising platform for creating distinct Majorana zero modes in magnetic vortices in a single material and at relatively high temperatures. The magnetic field-induced Abrikosov vortex lattice makes it difficult to braid a set of Majorana zero modes or to study the fusion of a Majorana doublet due to overlapping wave functions. Here we report the observation of the proposed quantum anomalous vortex with integer quantized vortex core states and Majorana zero mode induced by magnetic Fe adatoms deposited on the surface and the realization of its fusion with a nearby field-induced Majorana vortex in iron-based superconductor FeTe0.55Se0.45. We also observe vortex-free Yu-Shiba-Rusinov bound states at the Fe adatoms with a weaker coupling to the substrate, and discover a reversible transition between Yu-Shiba-Rusinov states and Majorana zero mode by manipulating the exchange coupling strength. The dual origin of the Majorana zero modes, from magnetic adatoms and external magnetic field, provides a new single-material platform for studying their interactions and braiding in superconductors bearing topological band structures.

scholarly journals ON THE PRIMORDIAL MAGNETIC FIELD FROM DOMAIN WALLS

2003 ◽  
Vol 12 (04) ◽  
pp. 663-666 ◽  
Author(s):  
P. CEA ◽  
L. TEDESCO
Keyword(s):  
Magnetic Field ◽  
Energy Density ◽  
Vacuum Energy ◽  
Domain Walls ◽  
Zero Mode ◽  
Vacuum Energy Density ◽  
Zero Modes ◽  
Careful Treatment ◽  
Primordial Magnetic Field

In this paper we discuss once more the zero mode contribution to the vacuum energy density. We show that a careful treatment of the zero modes leads to the conclusion that domain walls may be ferromagnetic, and could generate a magnetic field of cosmological interest.

scholarly journals A comment on instantons and their fermion zero modes in adjoint QCD_2

2021 ◽  
Vol 10 (6) ◽  
Author(s):  
Andrei Smilga
Keyword(s):  
Magnetic Flux ◽  
Gauge Field ◽  
Gauge Group ◽  
Wide Class ◽  
Zero Mode ◽  
Field Configuration ◽  
Integral Invariant ◽  
Zero Modes ◽  
Topological Sector ◽  
Left Handed

The adjoint 2-dimensional QCD with the gauge group SU(N)/Z_NSU(N)/ZN admits topologically nontrivial gauge field configurations associated with nontrivial \pi_1[SU(N)/Z_N] = Z_Nπ1[SU(N)/ZN]=ZN. The topological sectors are labelled by an integer k=0,\ldots, N-1k=0,…,N−1. However, in contrast to QED_2QED2 and QCD_4QCD4, this topology is not associated with an integral invariant like the magnetic flux or Pontryagin index. These instantons may admit fermion zero modes, but there is always an equal number of left-handed and right-handed modes, so that the Atiyah-Singer theorem, which determines in other cases the number of the modes, does not apply. The mod. 2 argument [1] suggests that, for a generic gauge field configuration, there is either a single doublet of such zero modes or no modes whatsoever. However, the known solution of the Dirac problem for a wide class of gauge field configurations indicates the presence of k(N-k) zero mode doublets in the topological sector k. In this note, we demonstrate in an explicit way that these modes are not robust under a generic enough deformation of the gauge background and confirm thereby the conjecture of Ref. [1]. The implications for the physics of this theory (screening vs. confinement issue) are briefly discussed.

scholarly journals Three-Dimensional Simulation Study of the Interactions of Three Successive CMEs during 4–5 November 1998

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 431
Author(s):  
Yufen Zhou ◽  
Xueshang Feng
Keyword(s):  
Magnetic Field ◽  
Interplanetary Space ◽  
Ambient Medium ◽  
Three Dimensional ◽  
The Third ◽  
Halo Cmes ◽  
Dimensional Simulation ◽  
The Individual ◽  
Basic Features ◽  
The Magnetic Field

In this paper, using a 3D magnetohydrodynamics (MHD) numerical simulation, we investigate the propagation and interaction of the three halo CMEs originating from the same active region during 4–5 November 1998 from the Sun to Earth. Firstly, we try to reproduce the observed basic features near Earth by a simple spherical plasmoid model. We find that the first component of the compound stream at 1 AU is associated to the first CME of the three halo CMEs. During the propagation in the interplanetary space, the third CME overtakes the second one. The two CMEs merge to a new, larger entity with complex internal structure. The magnetic field of the first CME in the three successive CMEs event is compressed by the following complex ejecta. The interaction between the second and third CME results in the deceleration of the third CME and the enhancement of the density, total magnetic field and south component of the magnetic field. In addition we study the contribution of a single CME to the final simulation results, as well as the effect of the CME–CME interactions on the propagation of an isolated CME and multiple CMEs. This is achieved by analysing a single CME with or without the presence of the preceding CMEs. Our results show that the CME moves faster in a less dense, faster medium generated by the interaction of the preceding CME with the ambient medium. In addition, we show that the CME–CME interactions can greatly alter the kinematics and magnetic structures of the individual events.

scholarly journals Chiral anomaly trapped in Weyl metals: Nonequilibrium valley polarization at zero magnetic field

2021 ◽  
Vol 11 (2) ◽  
Author(s):  
Pablo M. Perez-Piskunow ◽  
Nicandro Bovenzi ◽  
Anton Akhmerov ◽  
Maxim Breitkreiz
Keyword(s):  
Magnetic Field ◽  
Three Dimensional ◽  
Finite Size ◽  
Surface States ◽  
Direct Consequence ◽  
Field Application ◽  
Zero Magnetic Field ◽  
Chiral Anomaly ◽  
Valley Polarization ◽  
Disorder Potential

In Weyl semimetals, the application of parallel electric and magnetic fields leads to valley polarization---an occupation disbalance of valleys of opposite chirality---a direct consequence of the chiral anomaly. In this work, we present numerical tools to explore such nonequilibrium effects in spatially confined three-dimensional systems with a variable disorder potential, giving exact solutions to leading order in the disorder potential and the applied electric field. Application to a Weyl-metal slab shows that valley polarization also occurs without an external magnetic field as an effect of chiral anomaly ``trapping'': Spatial confinement produces chiral bulk states, which enable the valley polarization in a similar way as the chiral states induced by a magnetic field. Despite its finite-size origin, the valley polarization can persist up to macroscopic length scales if the disorder potential is sufficiently long ranged, so that direct inter-valley scattering is suppressed and the relaxation then goes via the Fermi-arc surface states.

scholarly journals Observation of magnetic adatom-induced Majorana vortex and its hybridization with field-induced Majorana vortex in an iron-based superconductor

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Peng Fan ◽  
Fazhi Yang ◽  
Guojian Qian ◽  
Hui Chen ◽  
Yu-Yang Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Bound States ◽  
Zero Mode ◽  
Fault Tolerant ◽  
Abrikosov Vortex ◽  
Zero Modes ◽  
Topological Quantum ◽  
Iron Based ◽  
Dual Origin ◽  
Single Material

AbstractBraiding Majorana zero modes is essential for fault-tolerant topological quantum computing. Iron-based superconductors with nontrivial band topology have recently emerged as a surprisingly promising platform for creating distinct Majorana zero modes in magnetic vortices in a single material and at relatively high temperatures. The magnetic field-induced Abrikosov vortex lattice makes it difficult to braid a set of Majorana zero modes or to study the coupling of a Majorana doublet due to overlapping wave functions. Here we report the observation of the proposed quantum anomalous vortex with integer quantized vortex core states and the Majorana zero mode induced by magnetic Fe adatoms deposited on the surface. We observe its hybridization with a nearby field-induced Majorana vortex in iron-based superconductor FeTe0.55Se0.45. We also observe vortex-free Yu-Shiba-Rusinov bound states at the Fe adatoms with a weaker coupling to the substrate, and discover a reversible transition between Yu-Shiba-Rusinov states and Majorana zero mode by manipulating the exchange coupling strength. The dual origin of the Majorana zero modes, from magnetic adatoms and external magnetic field, provides a new single-material platform for studying their interactions and braiding in superconductors bearing topological band structures.

Crystal Structure Analysis of Cu-Zr Alloys by Convergent Beam Diffraction

1981 ◽  
Vol 39 ◽  
pp. 354-355
Author(s):  
A. F. Marshall ◽  
J. W. Steeds ◽  
D. Bouchet ◽  
S. L. Shinde ◽  
R. G. Walmsley
Keyword(s):  
Crystal Structure ◽  
Point Group ◽  
Intermetallic Phase ◽  
Three Dimensional ◽  
Crystal Structure Analysis ◽  
Ion Milling ◽  
Composition And Structure ◽  
Unit Cells ◽  
Sputter Deposited ◽  
Convergent Beam

Convergent beam electron diffraction is a powerful technique for determining the crystal structure of a material in TEM. In this paper we have applied it to the study of the intermetallic phases in the Cu-rich end of the Cu-Zr system. These phases are highly ordered. Their composition and structure has been previously studied by microprobe and x-ray diffraction with sometimes conflicting results.The crystalline phases were obtained by annealing amorphous sputter-deposited Cu-Zr. Specimens were thinned for TEM by ion milling and observed in a Philips EM 400. Due to the large unit cells involved, a small convergence angle of diffraction was used; however, the three-dimensional lattice and symmetry information of convergent beam microdiffraction patterns is still present. The results are as follows:1) 21 at% Zr in Cu: annealed at 500°C for 5 hours. An intermetallic phase, Cu3.6Zr (21.7% Zr), space group P6/m has been proposed near this composition (2). The major phase of our annealed material was hexagonal with a point group determined as 6/m.

Semi-automated methods for 3-D reconstruction of macromolecular complexes

1995 ◽  
Vol 53 ◽  
pp. 42-43
Author(s):  
B. Carragher ◽  
M. Whittaker
Keyword(s):  
Three Dimensional ◽  
Time Saving ◽  
Macromolecular Complexes ◽  
Symmetry Properties ◽  
Dimensional Reconstruction ◽  
Experienced Operator ◽  
Projection Images ◽  
The Individual ◽  
Natural Symmetry

Techniques for three-dimensional reconstruction of macromolecular complexes from electron micrographs have been successfully used for many years. These include methods which take advantage of the natural symmetry properties of the structure (for example helical or icosahedral) as well as those that use single axis or other tilting geometries to reconstruct from a set of projection images. These techniques have traditionally relied on a very experienced operator to manually perform the often numerous and time consuming steps required to obtain the final reconstruction. While the guidance and oversight of an experienced and critical operator will always be an essential component of these techniques, recent advances in computer technology, microprocessor controlled microscopes and the availability of high quality CCD cameras have provided the means to automate many of the individual steps.During the acquisition of data automation provides benefits not only in terms of convenience and time saving but also in circumstances where manual procedures limit the quality of the final reconstruction.

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