Magnetic-field-induced robust zero Hall plateau state in MnBi2Te4 Chern insulator

AbstractThe intrinsic antiferromagnetic topological insulator MnBi2Te4 provides an ideal platform for exploring exotic topological quantum phenomena. Recently, the Chern insulator and axion insulator phases have been realized in few-layer MnBi2Te4 devices at low magnetic field regime. However, the fate of MnBi2Te4 in high magnetic field has never been explored in experiment. In this work, we report transport studies of exfoliated MnBi2Te4 flakes in pulsed magnetic fields up to 61.5 T. In the high-field limit, the Chern insulator phase with Chern number C = −1 evolves into a robust zero Hall resistance plateau state. Nonlocal transport measurements and theoretical calculations demonstrate that the charge transport in the zero Hall plateau state is conducted by two counter-propagating edge states that arise from the combined effects of Landau levels and large Zeeman effect in strong magnetic fields. Our result demonstrates the intricate interplay among intrinsic magnetic order, external magnetic field, and nontrivial band topology in MnBi2Te4.

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19. Astrophysical applications of selective magnetic rotation

Symposium - International Astronomical Union ◽

10.1017/s0074180900237753 ◽

1958 ◽

Vol 6 ◽

pp. 166-168

Author(s):

Y. öhman

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Zeeman Effect ◽

Emission Lines ◽

Absorption Lines ◽

Magnetic Rotation ◽

Double Refraction ◽

Line Absorption ◽

Complicated Process ◽

The Magnetic Field

When measuring the magnetic fields of sunspots the astronomer assumes that the magnetic field revealed by the inverse Zeeman effect is the same as if the splitting were produced by emission lines instead of absorption lines. No doubt this is in general a very fair approximation, but we have reason to remember sometimes that line absorption in the presence of magnetic fields is a very complicated process. In the immediate neighbourhood of absorption lines effects of magnetic rotation of the plane of polarization and magnetic double refraction may appear in the spectrum.

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Magnetic fields of rapidly oscillating Ap stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100117099 ◽

1993 ◽

Vol 139 ◽

pp. 132-132

Author(s):

G. Mathys

Keyword(s):

Magnetic Field ◽

High Resolution ◽

Magnetic Fields ◽

Zeeman Effect ◽

Rotation Frequency ◽

Spectral Lines ◽

Driving Mechanism ◽

Line Splitting ◽

Ap Stars ◽

The Magnetic Field

Magnetic field appears to play a major role in the pulsations of rapidly oscillating Ap (roAp) stars. Understanding of the behaviour of these objects thus requires knowledge of their magnetic field. Such knowledge is in particular essential to interpret the modulation of the amplitude of the photometric variations (with a frequency very close to the rotation frequency of the star) and to understand the driving mechanism of the pulsation. Therefore, a systematic programme of study of the magnetic field of roAp stars has been started, of which preliminary (and still very partial) results are presented here.Magnetic fields of Ap stars can be diagnosed from the Zeeman effect that they induced in spectral lines either from the observation of line-splitting in high-resolution unpolarized spectra (which only occurs in favourable circumstances) or from the observation of circular polarization of the lines in medium- to high-resolution spectra.

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Large discrete jumps observed in the transition between Chern states in a ferromagnetic topological insulator

Science Advances ◽

10.1126/sciadv.1600167 ◽

2016 ◽

Vol 2 (7) ◽

pp. e1600167 ◽

Cited By ~ 36

Author(s):

Minhao Liu ◽

Wudi Wang ◽

Anthony R. Richardella ◽

Abhinav Kandala ◽

Jian Li ◽

...

Keyword(s):

Magnetic Field ◽

Metastable State ◽

Large Fraction ◽

Surface States ◽

Anomalous Hall Effect ◽

Escape Rate ◽

Zero Magnetic Field ◽

Hall Resistance ◽

Edge States ◽

Longitudinal Resistance

A striking prediction in topological insulators is the appearance of the quantized Hall resistance when the surface states are magnetized. The surface Dirac states become gapped everywhere on the surface, but chiral edge states remain on the edges. In an applied current, the edge states produce a quantized Hall resistance that equals the Chern numberC= ±1 (in natural units), even in zero magnetic field. This quantum anomalous Hall effect was observed by Changet al. With reversal of the magnetic field, the system is trapped in a metastable state because of magnetic anisotropy. We investigate how the system escapes the metastable state at low temperatures (10 to 200 mK). When the dissipation (measured by the longitudinal resistance) is ultralow, we find that the system escapes by making a few very rapid transitions, as detected by large jumps in the Hall and longitudinal resistances. Using the field at which the initial jump occurs to estimate the escape rate, we find that raising the temperature strongly suppresses the rate. From a detailed map of the resistance versus gate voltage and temperature, we show that dissipation strongly affects the escape rate. We compare the observations with dissipative quantum tunneling predictions. In the ultralow dissipation regime, two temperature scales (T1~ 70 mK andT2~ 145 mK) exist, between which jumps can be observed. The jumps display a spatial correlation that extends over a large fraction of the sample.

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A Synthesized Method for Solving the 180° Ambiguity of Solar Transverse Magnetic Field

International Astronomical Union Colloquium ◽

10.1017/s0252921100029638 ◽

1993 ◽

Vol 141 ◽

pp. 461-464

Author(s):

Wang Huaning ◽

Lin Yuanzhang

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Transverse Magnetic Field ◽

Field Model ◽

Zeeman Effect ◽

Free Field ◽

Active Regions ◽

Transverse Magnetic ◽

Vector Magnetograms ◽

Divergence Equation

The 180° ambiguity of the transverse magnetic field measured by a heliomagnetograph is an intrinsic problem due to the linear polarization in Zeeman effect(Harvey, 1969). Thus we have to make use of some criteria for calibrating the transverse magnetic fields in vector magnetograms. Up to now, a few criteria have been suggested by some solar physicists (Harvey, 1969; Krall et al., 1982; Sakurai et al., 1985; Aly, 1989; Wu and Ai, 1990; Canfield et al., 1991. The existing criteria could be classified as observational criteria and mathematical criteria. The former is based on the observation facts, such as the fibrils and the filaments in solar filtergrams, and the latter is derived from the mathematical model of solar magnetic field, such as divergence equation (∆. B = 0), potential field model and force-free field model. These criteria, however, are not applicable to all solar active regions, especially to those with complicated magnetic fields. For this reason, we suggest a synthesized method for calibrating the transverse magnetic fields in solar vector magnetograms.

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Quantum Hall–based superconducting interference device

Science Advances ◽

10.1126/sciadv.aaw8693 ◽

2019 ◽

Vol 5 (9) ◽

pp. eaaw8693 ◽

Cited By ~ 4

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.

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Atomic-scale interface engineering of Majorana edge modes in a 2D magnet-superconductor hybrid system

Science Advances ◽

10.1126/sciadv.aav6600 ◽

2019 ◽

Vol 5 (7) ◽

pp. eaav6600 ◽

Cited By ~ 33

Author(s):

Alexandra Palacio-Morales ◽

Eric Mascot ◽

Sagen Cocklin ◽

Howon Kim ◽

Stephan Rachel ◽

...

Keyword(s):

Hybrid System ◽

Theoretical Calculations ◽

Real Space ◽

Scanning Tunneling Spectroscopy ◽

Atomic Scale ◽

Scanning Tunneling ◽

Edge States ◽

Interface Engineering ◽

New Paradigm ◽

Topological Quantum

Topological superconductors are predicted to harbor exotic boundary states—Majorana zero-energy modes—whose non-Abelian braiding statistics present a new paradigm for the realization of topological quantum computing. Using low-temperature scanning tunneling spectroscopy, here, we report on the direct real-space visualization of chiral Majorana edge states in a monolayer topological superconductor, a prototypical magnet-superconductor hybrid system composed of nanoscale Fe islands of monoatomic height on a Re(0001)-O(2 × 1) surface. In particular, we demonstrate that interface engineering by an atomically thin oxide layer is crucial for driving the hybrid system into a topologically nontrivial state as confirmed by theoretical calculations of the topological invariant, the Chern number.

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

Light Science & Applications ◽

10.1038/s41377-020-00377-6 ◽

2020 ◽

Vol 9 (1) ◽

Cited By ~ 2

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.

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Search for surface magnetic fields in Mira stars: first results on χ Cyg

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314002579 ◽

2013 ◽

Vol 9 (S302) ◽

pp. 385-388 ◽

Cited By ~ 1

Author(s):

Agnès Lèbre ◽

Michel Aurière ◽

Nicolas Fabas ◽

Denis Gillet ◽

Fabrice Herpin ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Zeeman Effect ◽

Stellar Atmosphere ◽

Asymptotic Giant Branch ◽

Photospheric Level ◽

First Results ◽

Weak Surface ◽

Surface Fields ◽

The Magnetic Field

AbstractSo far, surface magnetic fields have never been reported on Mira stars, while observational facilities allowing detection and measurement of weak surface fields through the Zeeman effect have become available. Then, in order to complete the knowledge of the magnetic field and of its influence during the transition from Asymptotic Giant Branch (AGB) to Planetary Nebulae (PN) stages, we have undertaken a search for magnetic fields at the surface of Miras. We present the first spectropolarimetric observations (performed with the Narval instrument at Télescope Bernard Lyot-TBL, Pic du Midi, France) of the S-type Mira star χ Cyg. We have detected a polarimetric signal in the Stokes V spectra and we have established its Zeeman origin. We claim that it is likely to be related to a weak magnetic field present at the photospheric level and in the lower part of the stellar atmosphere. The origin of this magnetic field is discussed in the framework of shock waves periodically propagating throughout the atmosphere of a Mira.

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roAp stars

Highlights of Astronomy ◽

10.1017/s1539299600011461 ◽

1995 ◽

Vol 10 ◽

pp. 338-340

Author(s):

D. Kurtz ◽

P. Martinez

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Field Strength ◽

Magnetic Field Strength ◽

Rotation Axis ◽

Zeeman Effect ◽

Spectral Lines ◽

Effective Magnetic Field ◽

Surface Magnetic Field ◽

Ap Stars

Among the A stars there is a subclass of peculiar stars, the Ap stars, which show strongly enhanced spectral lines of the Fe peak, rare earth and lanthanide elements. These stars have global surface magnetic fields several orders of magnitude larger than that of the Sun, 0.3 to 30 kGauss is the measured range. For stars with the strongest magnetic fields, the spectral lines are split by the Zeeman Effect and the surface magnetic field strength can be measured. Generally, though, the magnetic fields are not strong enough for the magnetic splitting to exceed other sources of line broadening. In these cases residual polarization differences between the red and blue wings of the spectral lines give a measure of the effective magnetic field strength - the integral of the longitudinal component of the global magnetic field over the visible hemisphere, weighted by limb-darkening. In the Ap stars the effective magnetic field strengths vary with rotation. This is well understood in terms of the oblique rotator model in which the magnetic axis is oblique to the rotation axis, so that the magnetic field is seen from varying aspect with rotation.

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QUENCHING OF THE HALL RESISTANCE IN A NOVEL GEOMETRY

Modern Physics Letters B ◽

10.1142/s0217984991000046 ◽

1991 ◽

Vol 05 (01) ◽

pp. 21-37

Author(s):

A.M. CHANG

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Electron Beams ◽

Hall Resistance ◽

Geometric Structures ◽

Ballistic Electron ◽

Junction Geometry ◽

Side Walls ◽

Low Magnetic Field ◽

Heterostructure Devices

We review experiments on the observation of Hall resistance anomalies in ballistic Hall junctions of novel geometries, in submicron GaAs-Al x Ga 1−x As heterostructure devices. We demonstrate that the low magnetic field Hall resistance is greatly influenced by the junction geometry, and that particular geometries are required to give rise to a phenomenon known as “quenching” of the Hall resistance where the conventional linear Hall resistance is suppressed to nearly zero, and to a related plateau feature at slightly higher magnetic fields, known as the “last plateau.” These anomalies are explained in terms of the collimation of ballistic electron beams by specific geometric structures and the scattering properties of the Hall junction side walls.

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