Nonlinear optical Hall effect in Weyl semimetal WTe2

Abstract The ordinary Hall effect refers to generation of a transverse voltage upon exertion of an electric field in the presence of an out-of-plane magnetic field. While a linear Hall effect is commonly observed in systems with breaking time-reversal symmetry via an applied external magnetic field or their intrinsic magnetization1, 2, a nonlinear Hall effect can generically occur in non-magnetic systems associated with a nonvanishing Berry curvature dipole3. Here we report, observations of a nonlinear optical Hall effect in a Weyl semimetal WTe2 without an applied magnetic field at room temperature. We observe an optical Hall effect resulting in a polarization rotation of the reflected light, referred to as the nonlinear Kerr rotation. The nonlinear Kerr rotation linearly depends on the charge current and optical power, which manifests the fourth-order nonlinearity. We quantitatively determine the fourth-order susceptibility, which exhibits strong anisotropy depending on the directions of the charge current and the light polarization. Employing symmetry analysis of Berry curvature multipoles, we demonstrate that the nonlinear Kerr rotations can arise from the Berry curvature hexapole allowed by the crystalline symmetries of WTe2. There also exist marginal signals that are incompatible with the symmetries, which suggest a hidden phase associated with the nonlinear process.

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Unconventional Hall effect induced by Berry curvature

National Science Review ◽

10.1093/nsr/nwaa163 ◽

2020 ◽

Vol 7 (12) ◽

pp. 1879-1885 ◽

Cited By ~ 1

Author(s):

Jun Ge ◽

Da Ma ◽

Yanzhao Liu ◽

Huichao Wang ◽

Yanan Li ◽

...

Keyword(s):

Magnetic Field ◽

Solid State ◽

Theoretical Analysis ◽

Hall Effect ◽

Transport Properties ◽

Berry Phase ◽

Phase Effect ◽

Berry Curvature ◽

Topological Materials ◽

Weyl Semimetal

Abstract Berry phase and Berry curvature play a key role in the development of topology in physics and do contribute to the transport properties in solid state systems. In this paper, we report the finding of novel nonzero Hall effect in topological material ZrTe5 flakes when the in-plane magnetic field is parallel and perpendicular to the current. Surprisingly, both symmetric and antisymmetric components with respect to magnetic field are detected in the in-plane Hall resistivity. Further theoretical analysis suggests that the magnetotransport properties originate from the anomalous velocity induced by Berry curvature in a tilted Weyl semimetal. Our work not only enriches the Hall family but also provides new insights into the Berry phase effect in topological materials.

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Berry curvature origin of the thickness-dependent anomalous Hall effect in a ferromagnetic Weyl semimetal

npj Quantum Materials ◽

10.1038/s41535-021-00315-8 ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

Yao Zhang ◽

Yuefeng Yin ◽

Guy Dubuis ◽

Tane Butler ◽

Nikhil V. Medhekar ◽

...

Keyword(s):

Band Structure ◽

Hall Effect ◽

Room Temperature ◽

Anomalous Hall Effect ◽

Berry Curvature ◽

Weyl Semimetal ◽

Hall Angle ◽

20 Nm ◽

Structure Calculations ◽

Spin Contribution

AbstractMagnetic Weyl semimetals with spontaneously broken time-reversal symmetry exhibit a large intrinsic anomalous Hall effect originating from the Berry curvature. To employ this large Hall current for room temperature topo-spintronics applications, it is necessary to fabricate these materials as thin or ultrathin films. Here, we experimentally demonstrate that Weyl semimetal Co2MnGa thin films (20–50 nm) show a large anomalous Hall angle ~11.4% at low temperature and ~9.7% at room temperature, which can be ascribed to the non-trivial topology of the band structure with large intrinsic Berry curvature. However, the anomalous Hall angle decreases significantly with thicknesses below 20 nm, which band structure calculations confirm is due to the reduction of the majority spin contribution to the Berry curvature. Our results suggest that Co2MnGa is an excellent material to realize room temperature topo-spintronics applications; however, the significant thickness dependence of the Berry curvature has important implications for thin-film device design.

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Ferroelectric nonlinear anomalous Hall effect in few-layer WTe2

npj Computational Materials ◽

10.1038/s41524-019-0257-1 ◽

2019 ◽

Vol 5 (1) ◽

Cited By ~ 6

Author(s):

Hua Wang ◽

Xiaofeng Qian

Keyword(s):

Magnetic Field ◽

Hall Effect ◽

Time Reversal ◽

First Principles ◽

Hall Current ◽

Anomalous Hall Effect ◽

New Order ◽

Berry Curvature ◽

Weyl Semimetals ◽

Nonlinear Quantum

AbstractUnder broken time reversal symmetry such as in the presence of external magnetic field or internal magnetization, a transverse voltage can be established in materials perpendicular to both longitudinal current and applied magnetic field, known as classical Hall effect. However, this symmetry constraint can be relaxed in the nonlinear regime, thereby enabling nonlinear anomalous Hall current in time-reversal invariant materials – an underexplored realm with exciting new opportunities beyond classical linear Hall effect. Here, using group theory and first-principles theory, we demonstrate a remarkable ferroelectric nonlinear anomalous Hall effect in time-reversal invariant few-layer WTe2 where nonlinear anomalous Hall current switches in odd-layer WTe2 except 1T′ monolayer while remaining invariant in even-layer WTe2 upon ferroelectric transition. This even-odd oscillation of ferroelectric nonlinear anomalous Hall effect was found to originate from the absence and presence of Berry curvature dipole reversal and shift dipole reversal due to distinct ferroelectric transformation in even and odd-layer WTe2. Our work not only treats Berry curvature dipole and shift dipole on an equal footing to account for intraband and interband contributions to nonlinear anomalous Hall effect, but also establishes Berry curvature dipole and shift dipole as new order parameters for noncentrosymmetric materials. The present findings suggest that ferroelectric metals and Weyl semimetals may offer unprecedented opportunities for the development of nonlinear quantum electronics.

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Strain-induced spontaneous Hall effect in an epitaxial thin film of a Luttinger semimetal

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1819489116 ◽

2019 ◽

Vol 116 (18) ◽

pp. 8803-8808 ◽

Cited By ~ 13

Author(s):

Takumi Ohtsuki ◽

Zhaoming Tian ◽

Akira Endo ◽

Mario Halim ◽

Shingo Katsumoto ◽

...

Keyword(s):

Magnetic Field ◽

Thin Film ◽

Hall Effect ◽

Temperature Scale ◽

Spontaneous Magnetization ◽

Chiral Anomaly ◽

Epitaxial Thin Film ◽

Negative Contribution ◽

Weyl Semimetal ◽

Brillouin Zone Center

Pyrochlore iridates have provided a plethora of novel phenomena owing to the combination of topology and correlation. Among them, much attention has been paid to Pr2Ir2O7, as it is known as a Luttinger semimetal characterized by quadratic band touching at the Brillouin zone center, suggesting that the topology of its electronic states can be tuned by a moderate lattice strain and external magnetic field. Here, we report that our epitaxial Pr2Ir2O7 thin films grown by solid-state epitaxy exhibit a spontaneous Hall effect that persists up to 50 K without having spontaneous magnetization within our experimental accuracy. This indicates that the system breaks the time reversal symmetry at a temperature scale that is too high for the magnetism to be due to Pr 4f moments and must be related to magnetic order of the iridium 5d electrons. Moreover, our analysis finds that the chiral anomaly induces the negative contribution to the magnetoresistance only when a magnetic field and the electric current are parallel to each other. Our results indicate that the strained part of the thin film forms a magnetic Weyl semimetal state.

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Berry curvature generation detected by Nernst responses in ferroelectric Weyl semimetal

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2111855118 ◽

2021 ◽

Vol 118 (44) ◽

pp. e2111855118

Author(s):

Cheng-Long Zhang ◽

Tian Liang ◽

M. S. Bahramy ◽

Naoki Ogawa ◽

Vilmos Kocsis ◽

...

Keyword(s):

Magnetic Field ◽

Mirror Symmetry ◽

Berry Curvature ◽

High Tunability ◽

Weyl Semimetal ◽

Weyl Semimetals ◽

Out Of Plane ◽

Field Geometry ◽

Transverse Thermoelectric Effect ◽

Ferroelectric Order

The quest for nonmagnetic Weyl semimetals with high tunability of phase has remained a demanding challenge. As the symmetry-breaking control parameter, the ferroelectric order can be steered to turn on/off the Weyl semimetals phase, adjust the band structures around the Fermi level, and enlarge/shrink the momentum separation of Weyl nodes which generate the Berry curvature as the emergent magnetic field. Here, we report the realization of a ferroelectric nonmagnetic Weyl semimetal based on indium-doped Pb1−xSnxTe alloy in which the underlying inversion symmetry as well as mirror symmetry are broken with the strength of ferroelectricity adjustable via tuning the indium doping level and Sn/Pb ratio. The transverse thermoelectric effect (i.e., Nernst effect), both for out-of-plane and in-plane magnetic field geometry, is exploited as a Berry curvature–sensitive experimental probe to manifest the generation of Berry curvature via the redistribution of Weyl nodes under magnetic fields. The results demonstrate a clean, nonmagnetic Weyl semimetal coupled with highly tunable ferroelectric order, providing an ideal platform for manipulating the Weyl fermions in nonmagnetic systems.

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Optical Hall effect measurement of coupled phonon mode - Landau Level transitions in epitaxial Graphene on silicon carbide

MRS Proceedings ◽

10.1557/opl.2013.811 ◽

2013 ◽

Vol 1505 ◽

Cited By ~ 1

Author(s):

P. Kühne ◽

A. Boosalis ◽

C. M. Herzinger ◽

L.O. Nyakiti ◽

V.D. Wheeler ◽

...

Keyword(s):

Magnetic Field ◽

Silicon Carbide ◽

Hall Effect ◽

Landau Level ◽

Quantitative Model ◽

Epitaxial Graphene ◽

Guided Wave ◽

Model Description ◽

Level Transition ◽

Optical Hall Effect

ABSTRACTWe report on mid-infrared (600 – 4000 cm-1), refection-type optical-Hall effect measurements on epitaxial graphene grown on C-face silicon carbide and present Landau-level transition features detected at 1.5 K as a function of magnetic field up to 8 Tesla. The Landau-level transitions are detected in reflection configuration at oblique incidence for wavenumbers below, across and above the silicon carbide reststrahlen range. Small Landau-level transition features are enhanced across the silicon carbide reststrahlen range due to surface-guided wave coupling with the electronic Landau-level transitions in the graphene layer. We analyze the spectral and magnetic-field dependencies of the coupled resonances, and compare our findings with previously reported Landau-level transitions measured in transmission configuration [4,5,6]. Additional features resemble transitions previously assigned to bilayer inclusion [21], as well as graphite [15]. We discuss a model description to account for the electromagnetic polarizability of the graphene layers, and which is sufficient for quantitative model calculation of the optical-Hall effect data.

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Generating a Topological Anomalous Hall Effect in a Nonmagnetic Conductor: An In-Plane Magnetic Field as a Direct Probe of the Berry Curvature

Physical Review Letters ◽

10.1103/physrevlett.126.256601 ◽

2021 ◽

Vol 126 (25) ◽

Author(s):

James H. Cullen ◽

Pankaj Bhalla ◽

E. Marcellina ◽

A. R. Hamilton ◽

Dimitrie Culcer

Keyword(s):

Magnetic Field ◽

Hall Effect ◽

Anomalous Hall Effect ◽

Berry Curvature

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MAGNETIC FIELD, PRESSURE AND TEMPERATURE DEPENDENT OPTICAL PROPERTIES IN A GaAs 9.0 P 1.0 QUANTUM DOT

JOURNAL OF ADVANCES IN PHYSICS ◽

10.24297/jap.v6i2.1791 ◽

2014 ◽

Vol 6 (2) ◽

pp. 1178-1190

Author(s):

A. JOHN PETER ◽

Ada Vinolin

Keyword(s):

Magnetic Field ◽

Optical Properties ◽

Quantum Dot ◽

Field Strength ◽

Magnetic Field Strength ◽

Photon Energy ◽

Nonlinear Optical ◽

Binding Energies ◽

Nonlinear Optical Properties ◽

Optical Rectification

Simultaneous effects of magnetic field, pressure and temperature on the exciton binding energies are found in a 9.0 1.0 6.0 4.0 GaAs P / GaAs P quantum dot. Numerical calculations are carried out taking into consideration of spatial confinement effect. The cylindrical system is taken in the present problem with the strain effects. The electronic properties and the optical properties are found with the combined effects of magnetic field strength, hydrostatic pressure and temperature values. The exciton binding energies and the nonlinear optical properties are carried out taking into consideration of geometrical confinement and the external perturbations.Compact density approach is employed to obtain the nonlinear optical properties. The optical rectification coefficient is obtained with the photon energy in the presence of pressure, temperature and external magnetic field strength. Pressure and temperature dependence on nonlinear opticalÂ susceptibilities of generation of second and third order harmonics as a function of incident photon energy are brought out in the influence of magnetic field strength. The result shows that the electronic and nonlinear optical properties are significantly modified by the applications of external perturbations in a 9.0 1.0 6.0 4.0 GaAs P / GaAs P quantum dot.

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Interface-induced sign reversal of the anomalous Hall effect in magnetic topological insulator heterostructures

Nature Communications ◽

10.1038/s41467-020-20349-z ◽

2021 ◽

Vol 12 (1) ◽

Cited By ~ 1

Author(s):

Fei Wang ◽

Xuepeng Wang ◽

Yi-Fan Zhao ◽

Di Xiao ◽

Ling-Jie Zhou ◽

...

Keyword(s):

Hall Effect ◽

Electric Fields ◽

First Principles ◽

Berry Phase ◽

Condensed Matter ◽

Anomalous Hall Effect ◽

First Principles Calculations ◽

Sign Reversal ◽

Berry Curvature ◽

Topological Materials

AbstractThe Berry phase picture provides important insights into the electronic properties of condensed matter systems. The intrinsic anomalous Hall (AH) effect can be understood as the consequence of non-zero Berry curvature in momentum space. Here, we fabricate TI/magnetic TI heterostructures and find that the sign of the AH effect in the magnetic TI layer can be changed from being positive to negative with increasing the thickness of the top TI layer. Our first-principles calculations show that the built-in electric fields at the TI/magnetic TI interface influence the band structure of the magnetic TI layer, and thus lead to a reconstruction of the Berry curvature in the heterostructure samples. Based on the interface-induced AH effect with a negative sign in TI/V-doped TI bilayer structures, we create an artificial “topological Hall effect”-like feature in the Hall trace of the V-doped TI/TI/Cr-doped TI sandwich heterostructures. Our study provides a new route to create the Berry curvature change in magnetic topological materials that may lead to potential technological applications.

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