Giant c-axis nonlinear anomalous Hall effect in Td-MoTe2 and WTe2

AbstractWhile the anomalous Hall effect can manifest even without an external magnetic field, time reversal symmetry is nonetheless still broken by the internal magnetization of the sample. Recently, it has been shown that certain materials without an inversion center allow for a nonlinear type of anomalous Hall effect whilst retaining time reversal symmetry. The effect may arise from either Berry curvature or through various asymmetric scattering mechanisms. Here, we report the observation of an extremely large c-axis nonlinear anomalous Hall effect in the non-centrosymmetric Td phase of MoTe2 and WTe2 without intrinsic magnetic order. We find that the effect is dominated by skew-scattering at higher temperatures combined with another scattering process active at low temperatures. Application of higher bias yields an extremely large Hall ratio of E⊥/E|| = 2.47 and corresponding anomalous Hall conductivity of order 8 × 107 S/m.

Download Full-text

Topological thermal Hall effect due to Weyl magnons

Canadian Journal of Physics ◽

10.1139/cjp-2018-0059 ◽

2018 ◽

Vol 96 (11) ◽

pp. 1216-1223 ◽

Cited By ~ 4

Author(s):

S.A. Owerre

Keyword(s):

Hall Effect ◽

Time Reversal ◽

Low Temperatures ◽

Three Dimensional ◽

Zero Magnetic Field ◽

Time Reversal Symmetry ◽

Frustrated Magnets ◽

Berry Curvature ◽

Theoretical Evidence ◽

Distribution Distance

We present the first theoretical evidence of zero magnetic field topological (anomalous) thermal Hall effect due to Weyl magnons in stacked noncoplanar frustrated kagomé antiferromagnets. The Weyl magnons in this system result from macroscopically broken time-reversal symmetry by the scalar spin chirality of noncoplanar chiral spin textures. Most importantly, they come from the lowest excitation, therefore they can be easily observed experimentally at low temperatures due to the population effect. Similar to electronic Weyl nodes close to the Fermi energy, Weyl magnon nodes at the lowest excitation are the most important. Indeed, we show that the topological (anomalous) thermal Hall effect in this system arises from nonvanishing Berry curvature due to Weyl magnon nodes at the lowest excitation, and it depends on their distribution (distance) in momentum space. The present result paves the way to directly probe low excitation Weyl magnons and macroscopically broken time-reversal symmetry in three-dimensional frustrated magnets with the anomalous thermal Hall effect.

Download Full-text

Quantum anomalous Hall effect in intrinsic magnetic topological insulator MnBi2Te4

Science ◽

10.1126/science.aax8156 ◽

2020 ◽

Vol 367 (6480) ◽

pp. 895-900 ◽

Cited By ~ 121

Author(s):

Yujun Deng ◽

Yijun Yu ◽

Meng Zhu Shi ◽

Zhongxun Guo ◽

Zihan Xu ◽

...

Keyword(s):

Magnetic Field ◽

Quantum Transport ◽

Topological Insulator ◽

Time Reversal ◽

Magnetic Order ◽

Anomalous Hall Effect ◽

Time Reversal Symmetry ◽

Zero Field ◽

Exotic States ◽

Ferromagnetic Layers

In a magnetic topological insulator, nontrivial band topology combines with magnetic order to produce exotic states of matter, such as quantum anomalous Hall (QAH) insulators and axion insulators. In this work, we probe quantum transport in MnBi2Te4 thin flakes—a topological insulator with intrinsic magnetic order. In this layered van der Waals crystal, the ferromagnetic layers couple antiparallel to each other; atomically thin MnBi2Te4, however, becomes ferromagnetic when the sample has an odd number of septuple layers. We observe a zero-field QAH effect in a five–septuple-layer specimen at 1.4 kelvin, and an external magnetic field further raises the quantization temperature to 6.5 kelvin by aligning all layers ferromagnetically. The results establish MnBi2Te4 as an ideal arena for further exploring various topological phenomena with a spontaneously broken time-reversal symmetry.

Download Full-text

Time-reversal symmetry breaking and spontaneous anomalous Hall effect in Fermi fluids

Physical Review B ◽

10.1103/physrevb.78.245122 ◽

2008 ◽

Vol 78 (24) ◽

Cited By ~ 51

Author(s):

Kai Sun ◽

Eduardo Fradkin

Keyword(s):

Symmetry Breaking ◽

Hall Effect ◽

Time Reversal ◽

Anomalous Hall Effect ◽

Time Reversal Symmetry ◽

Fermi Fluids

Download Full-text

Giant spontaneous Hall effect in a nonmagnetic Weyl–Kondo semimetal

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2013386118 ◽

2021 ◽

Vol 118 (8) ◽

pp. e2013386118 ◽

Cited By ~ 1

Author(s):

Sami Dzsaber ◽

Xinlin Yan ◽

Mathieu Taupin ◽

Gaku Eguchi ◽

Andrey Prokofiev ◽

...

Keyword(s):

Hall Effect ◽

Time Reversal ◽

Anomalous Hall Effect ◽

Time Reversal Symmetry ◽

Strong Electron ◽

Band Theory ◽

Fermion Systems ◽

Topological Quantum ◽

Interacting Systems ◽

Nontrivial Topology

Nontrivial topology in condensed-matter systems enriches quantum states of matter to go beyond either the classification into metals and insulators in terms of conventional band theory or that of symmetry-broken phases by Landau’s order parameter framework. So far, focus has been on weakly interacting systems, and little is known about the limit of strong electron correlations. Heavy fermion systems are a highly versatile platform to explore this regime. Here we report the discovery of a giant spontaneous Hall effect in the Kondo semimetal Ce3Bi4Pd3 that is noncentrosymmetric but preserves time-reversal symmetry. We attribute this finding to Weyl nodes—singularities of the Berry curvature—that emerge in the immediate vicinity of the Fermi level due to the Kondo interaction. We stress that this phenomenon is distinct from the previously detected anomalous Hall effect in materials with broken time-reversal symmetry; instead, it manifests an extreme topological response that requires a beyond-perturbation-theory description of the previously proposed nonlinear Hall effect. The large magnitude of the effect in even tiny electric and zero magnetic fields as well as its robust bulk nature may aid the exploitation in topological quantum devices.

Download Full-text

Giant nonlinear Hall effect in twisted bilayer WTe2

npj Quantum Materials ◽

10.1038/s41535-021-00403-9 ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

Zhihai He ◽

Hongming Weng

Keyword(s):

Fermi Level ◽

Hall Effect ◽

Time Reversal ◽

Large Amplitude ◽

Second Order ◽

Time Reversal Symmetry ◽

Inversion Symmetry ◽

Berry Curvature ◽

High Tunability

AbstractIn a system with broken inversion symmetry, a second-order nonlinear Hall effect can survive even in the presence of time-reversal symmetry. In this work, we show that a giant nonlinear Hall effect can exist in twisted bilayer WTe2 system. The Berry curvature dipole of twisted bilayer WTe2 (θ = 29.4°) can reach up to ~1400 Å, which is much larger than that in previously reported nonlinear Hall systems. In twisted bilayer WTe2 system, there exist abundant band anticrossings and band inversions around the Fermi level, which brings a complicated distribution of Berry curvature, and leads to the nonlinear Hall signals that exhibit dramatically oscillating behavior in this system. Its large amplitude and high tunability indicate that the twisted bilayer WTe2 can be an excellent platform for studying the nonlinear Hall effect.

Download Full-text

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.

Download Full-text

Loop Currents and Anomalous Hall Effect from Time-Reversal Symmetry-Breaking Superconductivity on the Honeycomb Lattice

Physical Review X ◽

10.1103/physrevx.9.031025 ◽

2019 ◽

Vol 9 (3) ◽

Cited By ~ 4

Author(s):

P. M. R. Brydon ◽

D. S. L. Abergel ◽

D. F. Agterberg ◽

Victor M. Yakovenko

Keyword(s):

Symmetry Breaking ◽

Hall Effect ◽

Time Reversal ◽

Anomalous Hall Effect ◽

Honeycomb Lattice ◽

Time Reversal Symmetry ◽

Loop Currents

Download Full-text

Quantum anomalous Hall effect in time-reversal-symmetry breaking topological insulators

Journal of Physics Condensed Matter ◽

10.1088/0953-8984/28/12/123002 ◽

2016 ◽

Vol 28 (12) ◽

pp. 123002 ◽

Cited By ~ 34

Author(s):

Cui-Zu Chang ◽

Mingda Li

Keyword(s):

Symmetry Breaking ◽

Hall Effect ◽

Time Reversal ◽

Topological Insulators ◽

Anomalous Hall Effect ◽

Time Reversal Symmetry ◽

Quantum Anomalous Hall Effect

Download Full-text

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.

Download Full-text