Chiral gauge field and axial anomaly in a Weyl semimetal

We show how the axial (chiral) anomaly induces a spin torque on the magnetization in magnetic Weyl semimetals. The anomaly produces an imbalance in left- and right-handed chirality carriers when non-orthogonal electric and magnetic fields are applied. Such imbalance generates a spin density which exerts a torque on the magnetization, the strength of which can be controlled by the intensity of the applied electric field. We show how this results in an electric control of the chirality of domain walls, as well as in an improvement of the domain wall dynamics, by delaying the onset of the Walker breakdown. The measurement of the electric field mediated changes in the domain wall chirality would constitute a direct proof of the axial anomaly. Additionally, we show how quantum fluctuations of electronic Fermi arc states bound to the domain wall naturally induce an effective magnetic anisotropy, allowing for high domain wall velocities even if the intrinsic anisotropy of the magnetic Weyl semimetal is small.

Download Full-text

Axial anomaly in the presence of the Aharonov-Bohm gauge field

Physical Review D ◽

10.1103/physrevd.50.5358 ◽

1994 ◽

Vol 50 (8) ◽

pp. 5358-5364 ◽

Cited By ~ 4

Author(s):

Paola Giacconi ◽

Stéphane Ouvry ◽

Roberto Soldati

Keyword(s):

Gauge Field ◽

Axial Anomaly ◽

Aharonov Bohm

Download Full-text

Detect axial gauge fields with a calorimeter

SciPost Physics Core ◽

10.21468/scipostphyscore.3.2.013 ◽

2020 ◽

Vol 3 (2) ◽

Author(s):

matteo Baggioli ◽

Maxim N. Chernodub ◽

Karl Landsteiner ◽

Maria Vozmediano

Keyword(s):

Specific Heat ◽

Sound Wave ◽

Experimental Verification ◽

Density Wave ◽

Gauge Fields ◽

Axial Anomaly ◽

Torsional Strain ◽

Weyl Semimetal ◽

Linear Behavior ◽

Weyl Semimetals

Torsional strain in Weyl semimetals excites a unidirectional chiral density wave propagating in the direction of the torsional vector. This gapless excitation, named the chiral sound wave, is generated by a particular realization of the axial anomaly via the triple-axial (AAA) anomalous diagram. We show that the presence of the torsion-generated chiral sound leads to a linear behavior of the specific heat of a Weyl semimetal and to an enhancement of the thermal conductivty at experimentally accessible temperatures. We also demonstrate that such an elastic twist lowers the temperature of the sample, thus generating a new, anomalous type of elasto-calorific effect. Measurements of these thermodynamical effects will provide experimental verification of the exotic triple-axial anomaly as well as the reality of the elastic pseudomagnetic fields in Weyl semimetals.

Download Full-text

A Weyl semimetal from AdS/CFT with flavour

Journal of High Energy Physics ◽

10.1007/jhep04(2021)162 ◽

2021 ◽

Vol 2021 (4) ◽

Author(s):

Kazem Bitaghsir Fadafan ◽

Andy O’Bannon ◽

Ronnie Rodgers ◽

Matthew Russell

Keyword(s):

Hall Conductivity ◽

Holographic Model ◽

Zero Temperature ◽

Top Down ◽

Spatial Direction ◽

Axial Anomaly ◽

Yang Mills ◽

First Order ◽

Weyl Semimetal ◽

Topological State

Abstract We construct a top-down holographic model of Weyl semimetal states using (3 + 1)-dimensional $$ \mathcal{N} $$ N = 4 supersymmetric SU(Nc) Yang-Mills theory, at large Nc and strong coupling, coupled to a number Nf ≪ Nc of $$ \mathcal{N} $$ N = 2 hypermultiplets with mass m. A U(1) subgroup of the R-symmetry acts on the hypermultiplet fermions as an axial symmetry. In the presence of a constant external axial gauge field in a spatial direction, b, we find the defining characteristic of a Weyl semi-metal: a quantum phase transition as m/b increases, from a topological state with non-zero anomalous Hall conductivity to a trivial insulator. The transition is first order. Remarkably, the anomalous Hall conductivity is independent of the hypermultiplet mass, taking the value dictated by the axial anomaly. At non-zero temperature the transition remains first order, and the anomalous Hall conductivity acquires non-trivial dependence on the hypermultiplet mass and temperature.

Download Full-text

Two-dimensional Tunable Dirac/Weyl Semimetal in Non-Abelian Gauge Field

Scientific Reports ◽

10.1038/s41598-019-54670-5 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 3

Author(s):

Yaowu Guo ◽

Zhi Lin ◽

Jia-Qiang Zhao ◽

Jie Lou ◽

Yan Chen

Keyword(s):

Gauge Field ◽

Fermi Energy ◽

Berry Phase ◽

Beat Frequency ◽

Three Dimensional ◽

High Energy ◽

Fermi Velocity ◽

Energy Bands ◽

Abelian Gauge ◽

Weyl Semimetal

AbstractThree-dimensional(3D) Weyl semimetal(WSM) with linear energy spectra has attracted significant interest. Especially they have been observed experimentally in several solid materials with the breaking of inversion symmetry. Here we predict a new family of particle-hole($${\mathscr{C}}$$C) invariant 2D WSMs in the non-Abelian gauge field, which can emerge in the low energy bands being close to Fermi energy (dubbed Weyl-I) and the high energy bands being away from Fermi energy (dubbed Weyl-II), only when the time-reversal symmetry($${\mathscr{T}}$$T) of the 2D Dirac semimetal is broken in the presence of in-plane Zeeman fields. Moreover, a 2D Dirac node can split into a pair of Weyl nodes showing the same Berry phase, and the 2D WSM, being protected by $${\mathscr{T}}$$T symmetry, exhibits four Weyl-I nodes, whose energies are invariant with the variation of the magnetic field. The corresponding Fermi velocity and Berry connection have been calculated. Based on the 2D WSMs, we also examine inhomogeneous pairings of attractive Fermi gases and find a new kind of the LO states with the beat frequency. This 2D WSM provides a realistic and promising platform for exploring and manipulating exotic Weyl physics, which may increase the experimental feasibility in the context of ultracold atoms.

Download Full-text

CHIRAL SCHWINGER MODEL AT FINITE TEMPERATURE

Modern Physics Letters A ◽

10.1142/s0217732392002688 ◽

1992 ◽

Vol 07 (35) ◽

pp. 3303-3308 ◽

Cited By ~ 4

Author(s):

H. BOSCHI-FILHO ◽

C.P. NATIVIDADE

Keyword(s):

Gauge Field ◽

Finite Temperature ◽

Axial Anomaly ◽

Schwinger Model

We discuss the chiral Schwinger model at finite temperature using Fujikawa’s method. We solve this model exactly and show that the axial anomaly and the dynamically generated mass for the gauge field are temperature independent.

Download Full-text

Riemann–Weyl in Deleuze's Bergsonism and the Constitution of the Contemporary Physico-Mathematical Space

Deleuze Studies ◽

10.3366/dls.2015.0174 ◽

2015 ◽

Vol 9 (1) ◽

pp. 59-87 ◽

Cited By ~ 3

Author(s):

Martin Calamari

Keyword(s):

Field Theory ◽

Gauge Field ◽

Fibre Bundle ◽

History Of Mathematics ◽

Gauge Field Theory ◽

Contemporary Science ◽

Explicit Mention ◽

History Of ◽

Key Features ◽

Bernhard Riemann

In recent years, the ideas of the mathematician Bernhard Riemann (1826–66) have come to the fore as one of Deleuze's principal sources of inspiration in regard to his engagements with mathematics, and the history of mathematics. Nevertheless, some relevant aspects and implications of Deleuze's philosophical reception and appropriation of Riemann's thought remain unexplored. In the first part of the paper I will begin by reconsidering the first explicit mention of Riemann in Deleuze's work, namely, in the second chapter of Bergsonism (1966). In this context, as I intend to show first, Deleuze's synthesis of some key features of the Riemannian theory of multiplicities (manifolds) is entirely dependent, both textually and conceptually, on his reading of another prominent figure in the history of mathematics: Hermann Weyl (1885–1955). This aspect has been largely underestimated, if not entirely neglected. However, as I attempt to bring out in the second part of the paper, reframing the understanding of Deleuze's philosophical engagement with Riemann's mathematics through the Riemann–Weyl conjunction can allow us to disclose some unexplored aspects of Deleuze's further elaboration of his theory of multiplicities (rhizomatic multiplicities, smooth spaces) and profound confrontation with contemporary science (fibre bundle topology and gauge field theory). This finally permits delineation of a correlation between Deleuze's plane of immanence and the contemporary physico-mathematical space of fundamental interactions.

Download Full-text