scholarly journals Direct observation of photonic Landau levels and helical edge states in strained honeycomb lattices

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Omar Jamadi ◽  
Elena Rozas ◽  
Grazia Salerno ◽  
Marijana Milićević ◽  
Tomoki Ozawa ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Symmetry Breaking ◽  
Distinctive Feature ◽  
Direct Evidence ◽  
Landau Levels ◽  
Honeycomb Lattice ◽  
Edge States ◽  
Photonic Lattices ◽  
Synthetic Magnetic Field

Abstract We report the realization of a synthetic magnetic field for photons and polaritons in a honeycomb lattice of coupled semiconductor micropillars. A strong synthetic field is induced in both the s and p orbital bands by engineering a uniaxial hopping gradient in the lattice, giving rise to the formation of Landau levels at the Dirac points. We provide direct evidence of the sublattice symmetry breaking of the lowest-order Landau level wavefunction, a distinctive feature of synthetic magnetic fields. Our realization implements helical edge states in the gap between n = 0 and n = ±1 Landau levels, experimentally demonstrating a novel way of engineering propagating edge states in photonic lattices. In light of recent advances in the enhancement of polariton–polariton nonlinearities, the Landau levels reported here are promising for the study of the interplay between pseudomagnetism and interactions in a photonic system.

scholarly journals Observation of fractional Chern insulators in a van der Waals heterostructure

Science ◽  
2018 ◽  
Vol 360 (6384) ◽  
pp. 62-66 ◽  
Author(s):  
Eric M. Spanton ◽  
Alexander A. Zibrov ◽  
Haoxin Zhou ◽  
Takashi Taniguchi ◽  
Kenji Watanabe ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Boron Nitride ◽  
Symmetry Breaking ◽  
Hexagonal Boron Nitride ◽  
Landau Levels ◽  
Topological Order ◽  
Hall Conductance ◽  
Van Der Waals Heterostructure ◽  
Ordered Phases ◽  
Chern Insulators

Topologically ordered phases are characterized by long-range quantum entanglement and fractional statistics rather than by symmetry breaking. First observed in a fractionally filled continuum Landau level, topological order has since been proposed to arise more generally at fractional fillings of topologically nontrivial Chern bands. Here we report the observation of gapped states at fractional fillings of Harper-Hofstadter bands arising from the interplay of a magnetic field and a superlattice potential in a bilayer graphene–hexagonal boron nitride heterostructure. We observed phases at fractional filling of bands with Chern indices C=−1, ±2, and ±3. Some of these phases, in C=−1 and C=2 bands, are characterized by fractional Hall conductance—that is, they are known as fractional Chern insulators and constitute an example of topological order beyond Landau levels.

scholarly journals DYNAMICAL SYMMETRY BREAKING IN THE EXTERNAL GRAVITATIONAL AND CONSTANT MAGNETIC FIELDS

1999 ◽  
Vol 14 (04) ◽  
pp. 481-503 ◽  
Author(s):  
T. INAGAKI ◽  
S. D. ODINTSOV ◽  
YU. I. SHIL'NOV
Keyword(s):  
Magnetic Field ◽  
Gravitational Field ◽  
Magnetic Fields ◽  
Symmetry Breaking ◽  
Effective Potential ◽  
Constant Magnetic Field ◽  
Dynamical Symmetry ◽  
Green Functions ◽  
Dynamical Symmetry Breaking ◽  
Njl Model

We investigate the effects of the external gravitational and constant magnetic fields to the dynamical symmetry breaking. As simple models of the dynamical symmetry breaking we consider the Nambu–Jona-Lasinio (NJL) model and the supersymmetric Nambu–Jona-Lasinio (SUSY NJL) model nonminimally interacting with the external gravitational field and minimally interacting with constant magnetic field. The explicit expressions for the scalar and spinor Green functions are found to the first order in the space–time curvature and exactly for a constant magnetic field. We obtain the effective potential of the above models from the Green functions in the magnetic field in curved space–time. Calculating the effective potential numerically with the varying curvature and/or magnetic fields we show the effects of the external gravitational and magnetic fields to the phase structure of the theories. In particular, increase of the curvature in the spontaneously broken phase of the chiral symmetry due to the fixed magnetic field makes this phase to be less broken. At the same time the strong magnetic field quickly induces chiral symmetry breaking even in the presence of fixed gravitational field within the nonbroken phase.

scholarly journals Quantum Hall–based superconducting interference device

2019 ◽  
Vol 5 (9) ◽  
pp. eaaw8693 ◽  
Author(s):  
Andrew Seredinski ◽  
Anne W. Draelos ◽  
Ethan G. Arnault ◽  
Ming-Tso Wei ◽  
Hengming Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Josephson Junction ◽  
Landau Level ◽  
Carrier Density ◽  
Filling Factor ◽  
Quantum Hall ◽  
Edge States ◽  
Highly Efficient ◽  
Wide Range

We present a study of a graphene-based Josephson junction with dedicated side gates carved from the same sheet of graphene as the junction itself. These side gates are highly efficient and allow us to modulate carrier density along either edge of the junction in a wide range. In particular, in magnetic fields in the 1- to 2-T range, we are able to populate the next Landau level, resulting in Hall plateaus with conductance that differs from the bulk filling factor. When counter-propagating quantum Hall edge states are introduced along either edge, we observe a supercurrent localized along that edge of the junction. Here, we study these supercurrents as a function of magnetic field and carrier density.

scholarly journals Zero modes, energy gap, and edge states of anisotropic honeycomb lattice in a magnetic field

2009 ◽  
Vol 80 (12) ◽  
Author(s):  
Kenta Esaki ◽  
Masatoshi Sato ◽  
Mahito Kohmoto ◽  
Bertrand I. Halperin
Keyword(s):  
Magnetic Field ◽  
Energy Gap ◽  
Honeycomb Lattice ◽  
Edge States ◽  
Zero Modes

scholarly journals Quantum Hall phases emerging from atom–photon interactions

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Alexander V. Poshakinskiy ◽  
Janet Zhong ◽  
Yongguan Ke ◽  
Nikita A. Olekhno ◽  
Chaohong Lee ◽  
...  
Keyword(s):  
Quantum Hall Effect ◽  
Quantum Electrodynamics ◽  
Quantum Hall ◽  
Landau Levels ◽  
Topological Order ◽  
Edge States ◽  
Quantum Structure ◽  
Many Body ◽  
Photon Interactions ◽  
Synthetic Magnetic Field

AbstractWe reveal the emergence of quantum Hall phases, topological edge states, spectral Landau levels, and Hofstadter butterfly spectra in the two-particle Hilbert space of an array of periodically spaced two-level atoms coupled to a waveguide (waveguide quantum electrodynamics). While the topological edge states of photons require fine-tuned spatial or temporal modulations of the parameters to generate synthetic magnetic fields and the quantum Hall effect, here we demonstrate that a synthetic magnetic field can be self-induced solely by atom–photon interactions. The fact that topological order can be self-induced in what is arguably the simplest possible quantum structure shows the richness of these waveguide quantum electrodynamics systems. We believe that our findings will advance several research disciplines including quantum optics, many-body physics, and nonlinear topological photonics, and that it will set an important reference point for the future experiments on qubit arrays and quantum simulators.

scholarly journals THE QUANTUM HALL EFFECT IN GRAPHENE

2012 ◽  
Vol 26 (13) ◽  
pp. 1250084 ◽  
Author(s):  
PAOLO CEA
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Fields ◽  
Numerical Simulations ◽  
Hall Effect ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
Landau Levels ◽  
Dynamical Generation ◽  
Dirac Sea

We investigate the quantum Hall effect in graphene. We argue that in graphene in presence of an external magnetic field there is dynamical generation of mass by a rearrangement of the Dirac sea. We show that the mechanism breaks the lattice valley degeneracy only for the n = 0 Landau levels and leads to the new observed ν = ±1 quantum Hall plateaus. We suggest that our result can be tested by means of numerical simulations of planar Quantum Electro Dynamics with dynamical fermions in an external magnetic fields on the lattice.

scholarly journals Propagators of charged particles in an external magnetic field, expanded over Landau levels

2015 ◽  
Vol 30 (24) ◽  
pp. 1550140 ◽  
Author(s):  
A. V. Kuznetsov ◽  
A. A. Okrugin ◽  
A. M. Shitova
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Fields ◽  
Standard Model ◽  
Constant Magnetic Field ◽  
Charged Particles ◽  
Landau Levels ◽  
The Standard Model ◽  
First Time

Various forms of expressions for the propagators of charged particles in a constant magnetic field that should be used for investigations of electroweak processes in an external uniform magnetic fields are discussed. Formulas for the propagators of the Standard Model charged [Formula: see text]- and scalar [Formula: see text]-bosons in an arbitrary [Formula: see text]-gauge, expanded over Landau levels, are derived for the first time.

Oscillatory Magneto-Conductance in Quantum Waveguides with Lateral Multi-Barrier Structures

1998 ◽  
Vol 12 (06) ◽  
pp. 653-661 ◽  
Author(s):  
Ben-Yuan Gu ◽  
Wei-Dong Sheng ◽  
Jian Wang
Keyword(s):  
Magnetic Field ◽  
Landau Levels ◽  
Tunneling Effect ◽  
Edge States ◽  
Quantum Devices ◽  
Quantum Waveguide ◽  
Localized State ◽  
Barrier Region ◽  
Potential Applications ◽  
Quantum Waveguides

The magneto-transport properties of a narrow quantum waveguide with lateral multi-barrier modulation are investigated theoretically. It is found that the magneto-conductance as a function of Fermi energy or magnetic field exhibits square-wave-like oscillations. In the presence of magnetic field, the edge states are formed near each barrier and the boundaries. Therefore, the number of edge states increases with the number of lateral barriers, leading to the increase of the propagating modes. On the other hand, owing to the tunneling effect a pair of edge states around the barrier region with opposite moving directions may be coupled and formed a circulating localized state, leading to the quenching of the related propagating states. The resulting dispersion relation exhibits oscillation structures superimposed on the bulk Landau levels. These novel conductance characteristics may provide potential applications to the fabrication of new quantum devices.

LANDAU LEVEL SPECTRUM FOR CHARGED PARTICLE IN A CLASS OF NON-UNIFORM MAGNETIC FIELDS

1993 ◽  
Vol 08 (06) ◽  
pp. 523-529 ◽  
Author(s):  
AVINASH KHARE ◽  
C. NAGARAJA KUMAR
Keyword(s):  
Magnetic Field ◽  
Charged Particle ◽  
Magnetic Fields ◽  
Landau Level ◽  
Wide Class ◽  
Uniform Magnetic Field ◽  
Landau Levels ◽  
Level Spectrum

The spectrum of a charged particle in uniform magnetic field consists of equally spaced Landau levels which are infinitely degenerate. We consider isospectral deformations of this problem and show that the spectrum is again equispaced but nondegenerate for a wide class of non-uniform magnetic fields.

scholarly journals PAIR PRODUCTION IN A TIME-DEPENDENT MAGNETIC FIELD

1999 ◽  
Vol 14 (18) ◽  
pp. 1183-1192 ◽  
Author(s):  
GIORGIO CALUCCI
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Pair Production ◽  
Rest Mass ◽  
Landau Levels ◽  
Time Dependent ◽  
Electron Positron ◽  
Astrophysical Objects ◽  
The Magnetic Field

The production of electron–positron pairs in a time-dependent magnetic field is estimated in the hypotheses that the magnetic field is uniform over large distances with respect to the pair localization and it is so strong that the spacing of the Landau levels is larger than the rest mass of the particles. This calculation is presented since it has been suggested that extremely intense and varying magnetic fields may be found around some astrophysical objects.

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