scholarly journals Unconventional Hall effect induced by Berry curvature

2020 ◽  
Vol 7 (12) ◽  
pp. 1879-1885 ◽  
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.

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

2021 ◽  
Vol 12 (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.

scholarly journals Nonlinear optical Hall effect in Weyl semimetal WTe2

2021 ◽  
Author(s):  
Young-Gwan Choi ◽  
Manh-Ha Doan ◽  
Youngkuk Kim ◽  
Gyung-Min Choi
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Fourth Order ◽  
Nonlinear Optical ◽  
Light Polarization ◽  
Kerr Rotation ◽  
Berry Curvature ◽  
Charge Current ◽  
Weyl Semimetal ◽  
Optical Hall Effect

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.

scholarly journals Quantized thermoelectric Hall effect induces giant power factor in a topological semimetal

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Fei Han ◽  
Nina Andrejevic ◽  
Thanh Nguyen ◽  
Vladyslav Kozii ◽  
Quynh T. Nguyen ◽  
...  
Keyword(s):  
Energy Harvesting ◽  
Hall Effect ◽  
Power Factor ◽  
Room Temperature ◽  
Waste Heat ◽  
Quantum Limit ◽  
Topological Materials ◽  
Weyl Semimetal ◽  
Topological Semimetals ◽  
Electronic Entropy

AbstractThermoelectrics are promising by directly generating electricity from waste heat. However, (sub-)room-temperature thermoelectrics have been a long-standing challenge due to vanishing electronic entropy at low temperatures. Topological materials offer a new avenue for energy harvesting applications. Recent theories predicted that topological semimetals at the quantum limit can lead to a large, non-saturating thermopower and a quantized thermoelectric Hall conductivity approaching a universal value. Here, we experimentally demonstrate the non-saturating thermopower and quantized thermoelectric Hall effect in the topological Weyl semimetal (WSM) tantalum phosphide (TaP). An ultrahigh longitudinal thermopower $$S_{xx} \sim 1.1 \times 10^3 \, \mu \, {\mathrm{V}} \, {\mathrm{K}}^{ - 1}$$ S x x ~ 1.1 × 1 0 3 μ V K − 1 and giant power factor $$\sim 525 \, \mu \, {\mathrm{W}} \, {\mathrm{cm}}^{ - 1} \, {\mathrm{K}}^{ - 2}$$ ~ 525 μ W cm − 1 K − 2 are observed at ~40 K, which is largely attributed to the quantized thermoelectric Hall effect. Our work highlights the unique quantized thermoelectric Hall effect realized in a WSM toward low-temperature energy harvesting applications.

scholarly journals Topological Bloch bands in graphene superlattices

2015 ◽  
Vol 112 (35) ◽  
pp. 10879-10883 ◽  
Author(s):  
Justin C. W. Song ◽  
Polnop Samutpraphoot ◽  
Leonid S. Levitov
Keyword(s):  
Boron Nitride ◽  
Hall Effect ◽  
Hexagonal Boron Nitride ◽  
Electrical Response ◽  
Model System ◽  
Topological Properties ◽  
Berry Curvature ◽  
Topological Materials ◽  
Highly Sensitive ◽  
Valley Hall Effect

We outline a designer approach to endow widely available plain materials with topological properties by stacking them atop other nontopological materials. The approach is illustrated with a model system comprising graphene stacked atop hexagonal boron nitride. In this case, the Berry curvature of the electron Bloch bands is highly sensitive to the stacking configuration. As a result, electron topology can be controlled by crystal axes alignment, granting a practical route to designer topological materials. Berry curvature manifests itself in transport via the valley Hall effect and long-range chargeless valley currents. The nonlocal electrical response mediated by such currents provides diagnostics for band topology.

INFLUENCE OF MAGNETIC FIELDS ON THE INTRINSIC SPIN HALL EFFECT IN TWO-DIMENSIONAL SYSTEMS

2009 ◽  
Vol 23 (12n13) ◽  
pp. 2566-2572 ◽  
Author(s):  
O. E. RAICHEV
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Hall Effect ◽  
Berry Phase ◽  
Zeeman Splitting ◽  
Hall Conductivity ◽  
Spin Hall Effect ◽  
Two Dimensional ◽  
The Magnetic Field ◽  
Spin Hall Conductivity

The influence of magnetic fields on the electron spin in solids involves two basic mechanisms. First, any magnetic field introduces the Zeeman splitting of electron states, thereby modifying spin precession. Second, since the magnetic field affects the electron motion in the plane perpendicular to the field, the spin dynamics is also modified, owing to the spin-orbit interaction. The theory predicts, as a consequence of this influence, unusual properties of the intrinsic spin-Hall effect in two-dimensional systems in the presence of magnetic fields. This paper describes non-monotonic dependence of the spin-Hall conductivity on the magnetic field and its enhancement in the case of weak disorder, as well as multiple jumps of the spin-Hall conductivity owing to the topological transitions (abrupt changes of the Berry phase) induced by the parallel magnetic field.

QUANTUM HALL EFFECT AND BERRY PHASE

1994 ◽  
Vol 08 (26) ◽  
pp. 1643-1653 ◽  
Author(s):  
DIPTI BANERJEE ◽  
PRATUL BANDYOPADHYAY
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Quantum Hall Effect ◽  
Berry Phase ◽  
Quantum Hall ◽  
Fractional Quantum Hall Effect ◽  
Fractional Quantum ◽  
Fractional Quantum Hall ◽  
Intense Magnetic Field ◽  
Topological Features

It is shown here that a particle in an intense magnetic field may acquire the Berry phase and the topological features associated with this phase may be taken to be responsible for both the integrally and fractionally quantized Hall effect. The two different manifestations of quantum Hall effect have been realized in a unified scheme where the electrons associated with the fractional quantum Hall effect are found to be in an excited state having higher angular momentum.

scholarly journals Transport Properties in Dense QCD Matter

Symmetry ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 366
Author(s):  
Toshitaka Tatsumi ◽  
Hiroaki Abuki
Keyword(s):  
Magnetic Field ◽  
Transport Properties ◽  
Quark Matter ◽  
Anomalous Hall Effect ◽  
Close Relation ◽  
Kubo Formula ◽  
Weyl Semimetal ◽  
Chiral Transition ◽  
Spectral Asymmetry ◽  
The Magnetic Field

Transport properties of dense QCD matter are discussed. Using the Kubo formula for conductivity, we discuss some topological aspects of quark matter during the chiral transition. The close relation to Weyl semimetal is pointed out and anomalous Hall effect is demonstrated to be possible. In particular, it is shown that the spectral asymmetry of the quasi-particles plays an important role for the Hall conductivity in the magnetic field.

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

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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