Berry curvature force and Lorentz force comparison in the magnetotransport of Weyl semimetals

2018 ◽  
Vol 98 (20) ◽  
Author(s):  
Muhammad Imran ◽  
Selman Hershfield
Keyword(s):  
Lorentz Force ◽  
Berry Curvature ◽  
Weyl Semimetals ◽  
Curvature Force

scholarly journals Absence of Hall effect due to Berry curvature in phase space

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Takehito Yokoyama
Keyword(s):  
Phase Space ◽  
Wave Packet ◽  
Hall Effect ◽  
Lorentz Force ◽  
Equations Of Motion ◽  
Electron Wave ◽  
Boltzmann Equations ◽  
Berry Curvature ◽  
Electron Wave Packet ◽  
Transverse Current

AbstractTransverse current due to Berry curvature in phase space is formulated based on the Boltzmann equations with the semiclassical equations of motion for an electron wave packet. It is shown that the Hall effect due to the phase space Berry curvature is absent because the contributions from “anomalous velocity” and “effective Lorentz force” are completely cancelled out.

scholarly journals Nonlinear transport in Weyl semimetals induced by Berry curvature dipole

2021 ◽  
Vol 103 (24) ◽  
Author(s):  
Chuanchang Zeng ◽  
Snehasish Nandy ◽  
Sumanta Tewari
Keyword(s):  
Nonlinear Transport ◽  
Berry Curvature ◽  
Weyl Semimetals

scholarly journals A Primer on Weyl Semimetals: Down the Discovery of Topological Phases

2021 ◽  
pp. 34-45
Author(s):  
Satyaki Kar ◽  
Arun M. Jayannavar
Keyword(s):  
Magnetic Monopole ◽  
Condensed Matter ◽  
Surface States ◽  
Berry Curvature ◽  
Fermi Arcs ◽  
Electric And Magnetic Fields ◽  
Weyl Semimetals ◽  
Topological Surface ◽  
Bulk Energy ◽  
Basic Features

Recently discovered Weyl semimetals (WSM) have found special place in topological condensed matter studies for they represent first example of massless Weyl fermions found in electronic condensed matter systems. A WSM shows gapless bulk energy spectra with Dirac-like point degeneracies, famously called Weyl nodes, which carry with themselves well defined chiralities and topologically protected chiral charges. One finds the Berry curvature of the Bloch bands to become singular, like in a magnetic monopole, at these Weyl nodes. Moreover, these systems feature topological surface states in the form of open Fermi arcs. In this review, we undergo a concise journey from graphene based Dirac physics to Weyl semimetals: the underlying Hamiltonians, their basic features and their unique response to external electric and magnetic fields in order to provide a basic walk-through of how the Weyl physics unfolded with time starting from the discovery of Graphene.

scholarly journals Ferroelectric nonlinear anomalous Hall effect in few-layer WTe2

2019 ◽  
Vol 5 (1) ◽  
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.

scholarly journals Tilting dependence and anisotropy of anomaly-related magnetoconductance in type-II Weyl semimetals

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Hiroaki Ishizuka ◽  
Naoto Nagaosa
Keyword(s):  
Fermi Level ◽  
Semiclassical Limit ◽  
Magnetic Effect ◽  
Type Ii ◽  
Berry Curvature ◽  
Chiral Magnetic Effect ◽  
Weyl Semimetals

Abstract We theoretically study chiral magnetic effect in type-II Weyl semimetals based on a concise formalism for the magnetoconductance in the semiclassical limit. Using the formula, we find that the anomaly-related current is generally dominated by the contribution from the Weyl nodes when the Fermi level is sufficiently close to the nodes. This is related to the fact that the current is proportional to the square of the Berry curvature, which enhances the contribution from the electrons around the Weyl nodes. The increase and the anisotropy of magnetoconductance induced by the tilting is also explained in a comprehensive way.

Strain-Engineered Nonlinear Hall Effect in HgTe

SPIN ◽  
2019 ◽  
Vol 09 (04) ◽  
pp. 1940017
Author(s):  
Cheng Chen ◽  
Huaiqiang Wang ◽  
Dinghui Wang ◽  
Haijun Zhang
Keyword(s):  
Transition Metal ◽  
Hall Effect ◽  
Transition Metal Dichalcogenides ◽  
Three Dimensional ◽  
Electronic Band ◽  
Berry Curvature ◽  
High Tunability ◽  
Weyl Semimetals ◽  
Metal Dichalcogenides ◽  
The Ideal

As paradigmatic phenomena, Hall effects have inspired tremendous studies of symmetry and topology in condensed matter physics. Intriguingly, a second-order nonlinear Hall effect was recently proposed in noncentrosymmetric materials even in the presence of time-reversal symmetry. This effect originates from the Berry curvature dipole of electronic band structures and was predicted in Dirac and Weyl materials such as transition metal dichalcogenides and Weyl semimetals. Although it has been experimentally verified in some transition metal dichalcogenides, no obvious observation of such effects has been reported in Weyl semimetals. Taking advantage of the ideal Weyl phase with no coexisting trivial bands at the Fermi level, we use strained HgTe as a concrete example to show that the ideal Weyl semimetal is a promising platform for demonstrating the nonlinear Hall effect. Based on numerical calculations of the Berry curvature dipole, it was found that the magnitude of nonlinear Hall effect can be simply engineered by in-plane strain. Our work provides a versatile platform with high tunability, which could greatly facilitate the study of nonlinear Hall effect in three-dimensional topological materials.

scholarly journals Influence of anisotropy, tilt and pairing of Weyl nodes: the Weyl semimetals TaAs, TaP, NbAs and NbP

2020 ◽  
Vol 93 (8) ◽  
Author(s):  
Davide Grassano ◽  
Olivia Pulci ◽  
Elena Cannuccia ◽  
Friedhelm Bechstedt
Keyword(s):  
Topological Properties ◽  
Strong Anisotropy ◽  
Berry Curvature ◽  
Electronic Spin ◽  
Weyl Semimetals ◽  
Connection Line ◽  
Spin Texture ◽  
Weyl Fermion ◽  
Topological Character ◽  
Conventional Picture

Abstract By means of ab initio band structure methods and model Hamiltonians we investigate the electronic, spin and topological properties of four monopnictides crystallizing in bct structure. We show that the Weyl bands around a WP W1 or W2 possess a strong anisotropy and tilt of the accompanying Dirac cones. These effects are larger for W2 nodes than for W1 ones. The node tilts and positions in energy space significantly influence the DOS of single-particle Weyl excitations. The node anisotropies destroy the conventional picture of (anti)parallel spin and wave vector of a Weyl fermion. This also holds for the Berry curvature around a node, while the monopole charges are independent as integrated quantities. The pairing of the nodes strongly modifies the spin texture and the Berry curvature for wave vectors in between the two nodes. Spin components may change their orientation. Integrals over planes perpendicular to the connection line yield finite Zak phases and winding numbers for planes between the two nodes, thereby indicating the topological character. Graphical abstract

scholarly journals Berry curvature generation detected by Nernst responses in ferroelectric Weyl semimetal

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.

Numerical Studies on Behavior of Lorentz-Force-Applied Boundary Layer in Supersonic Flow

2009 ◽  
Vol 129 (6) ◽  
pp. 831-839
Author(s):  
Keisuke Udagawa ◽  
Sadatake Tomioka ◽  
Hiroyuki Yamasaki
Keyword(s):  
Boundary Layer ◽  
Supersonic Flow ◽  
Lorentz Force ◽  
Numerical Studies
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