Positive Magnetoresistance and Chiral Anomaly in Exfoliated Type-II Weyl Semimetal Td-WTe2

Layered van der Waals semimetallic Td-WTe2, exhibiting intriguing properties which include non-saturating extreme positive magnetoresistance (MR) and tunable chiral anomaly, has emerged as a model topological type-II Weyl semimetal system. Here, ∼45 nm thick mechanically exfoliated flakes of Td-WTe2 are studied via atomic force microscopy, Raman spectroscopy, low-T/high-μ0H magnetotransport measurements and optical reflectivity. The contribution of anisotropy of the Fermi liquid state to the origin of the large positive transverse MR⊥ and the signature of chiral anomaly of the type-II Weyl Fermions are reported. The samples are found to be stable in air and no oxidation or degradation of the electronic properties is observed. A transverse MR⊥∼1200 % and an average carrier mobility of 5000 cm2V−1s−1 at T=5K for an applied perpendicular field μ0H⊥=7T are established. The system follows a Fermi liquid model for T≤50K and the anisotropy of the Fermi surface is concluded to be at the origin of the observed positive MR. Optical reflectivity measurements confirm the anisotropy of the electronic behaviour. The relative orientation of the crystal axes and of the applied electric and magnetic fields is proven to determine the observed chiral anomaly in the in-plane magnetotransport. The observed chiral anomaly in the WTe2 flakes is found to persist up to T=120K, a temperature at least four times higher than the ones reported to date.

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Impact of domain disorder on optoelectronic properties of layered semimetal MoTe2

2D Materials ◽

10.1088/2053-1583/ac3e03 ◽

2021 ◽

Author(s):

Maanwinder P. Singh ◽

Jonas Kiemle ◽

Ilkay Ozdemir ◽

Philipp Zimmermann ◽

Takashi Taniguchi ◽

...

Keyword(s):

Van Der Waals ◽

Topological Type ◽

Optoelectronic Properties ◽

Local Domain ◽

Type Ii ◽

Relaxation Dynamics ◽

Weyl Semimetal ◽

Ultrafast Relaxation ◽

Low Dimensional ◽

The Impact

Abstract We address the impact of crystal phase disorder on the generation of helicity-dependent photocurrents in layered MoTe2, which is one of the van der Waals materials to realize the topological type-II Weyl semimetal phase. Using scanning photocurrent microscopy, we spatially probe the phase transition and its hysteresis between the centrosymmetric, monoclinic 1T’ phase to the symmetry-broken, orthorhombic Td phase as a function of temperature. We ﬁnd a highly disordered photocurrent response in the intermediate temperature regime. Moreover, we demonstrate that helicity-dependent and ultrafast photocurrents in MoTe2 arise most likely from a local breaking of the electronic symmetries. Our results highlight the prospects of local domain morphologies and ultrafast relaxation dynamics on the optoelectronic properties of low-dimensional van der Waals circuits.

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Evidence for topological type-II Weyl semimetal WTe2

Nature Communications ◽

10.1038/s41467-017-02237-1 ◽

2017 ◽

Vol 8 (1) ◽

Cited By ~ 105

Author(s):

Peng Li ◽

Yan Wen ◽

Xin He ◽

Qiang Zhang ◽

Chuan Xia ◽

...

Keyword(s):

Topological Type ◽

Type Ii ◽

Weyl Semimetal

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Superconductivity in doped Weyl semimetal Mo0.9IR0.1Te2 with broken inversion symmetry

Superconductor Science and Technology ◽

10.1088/1361-6668/ac3b38 ◽

2021 ◽

Author(s):

Manasi Mandal ◽

Chandan Patra ◽

Anshu Kataria ◽

Suvodeep Paul ◽

Surajit Saha ◽

...

Keyword(s):

Hall Effect ◽

Chiral Anomaly ◽

Inversion Symmetry ◽

Type Ii ◽

Promising Candidate ◽

Planar Hall Effect ◽

Topological Superconductor ◽

Weyl Semimetal ◽

Type Ii Superconductivity ◽

Magneto Resistance

Abstract This work presents the emergence of superconductivity in Ir - doped Weyl semimetal T$_d$ - MoTe$_{2}$ with broken inversion symmetry. Chiral anomaly induced planar Hall effect and anisotropic magneto-resistance confirm the topological semimetallic nature of Mo$_{1-x}$Ir$_{x}$Te$_{2}$. Observation of weak anisotropic, moderately coupled type-II superconductivity in T$_d$ -Mo$_{1-x}$Ir$_{x}$Te$_{2}$ makes it a promising candidate for topological superconductor.

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Electric manipulation of domain walls in magnetic Weyl semimetals via the axial anomaly

SciPost Physics ◽

10.21468/scipostphys.10.5.102 ◽

2021 ◽

Vol 10 (5) ◽

Author(s):

Julia Hannukainen ◽

Alberto Cortijo ◽

Jens H Bardarson ◽

Yago Ferreiros

Keyword(s):

Domain Wall ◽

Electric Field ◽

Domain Walls ◽

Direct Proof ◽

Chiral Anomaly ◽

Axial Anomaly ◽

Domain Wall Dynamics ◽

Weyl Semimetal ◽

Electric And Magnetic Fields ◽

Weyl Semimetals

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.

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Localized spin-orbit polaron in magnetic Weyl semimetal Co3Sn2S2

Nature Communications ◽

10.1038/s41467-020-19440-2 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Yuqing Xing ◽

Jianlei Shen ◽

Hui Chen ◽

Li Huang ◽

Yuxiang Gao ◽

...

Keyword(s):

Surface States ◽

Chiral Anomaly ◽

Scanning Tunneling ◽

Spin Orbit ◽

Tunneling Microscopy ◽

Practical Applications ◽

Force Microscopy ◽

Weyl Semimetal ◽

Atomic Force ◽

Topological State

Abstract The kagome lattice Co3Sn2S2 exhibits the quintessential topological phenomena of a magnetic Weyl semimetal such as the chiral anomaly and Fermi-arc surface states. Probing its magnetic properties is crucial for understanding this correlated topological state. Here, using spin-polarized scanning tunneling microscopy/spectroscopy (STM/S) and non-contact atomic force microscopy (nc-AFM) combined with first-principle calculations, we report the discovery of localized spin-orbit polarons (SOPs) with three-fold rotation symmetry nucleated around single S-vacancies in Co3Sn2S2. The SOPs carry a magnetic moment and a large diamagnetic orbital magnetization of a possible topological origin associated relating to the diamagnetic circulating current around the S-vacancy. Appreciable magneto-elastic coupling of the SOP is detected by nc-AFM and STM. Our findings suggest that the SOPs can enhance magnetism and more robust time-reversal-symmetry-breaking topological phenomena. Controlled engineering of the SOPs may pave the way toward practical applications in functional quantum devices.

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Localized spin-orbit polaron in magnetic Weyl semimetal Co3Sn2S2

10.21203/rs.3.rs-53173/v1 ◽

2020 ◽

Cited By ~ 1

Author(s):

Yuqing Xing ◽

Jianlei Shen ◽

Hui Chen ◽

Li Huang ◽

Yuxiang Gao ◽

...

Keyword(s):

Surface States ◽

Chiral Anomaly ◽

Scanning Tunneling ◽

Spin Orbit ◽

Tunneling Microscopy ◽

Practical Applications ◽

Force Microscopy ◽

Weyl Semimetal ◽

Atomic Force ◽

Topological State

Abstract The kagome lattice Co3Sn2S2 exhibits the quintessential topological phenomena of a magnetic Weyl semimetal such as the chiral anomaly and Fermi-arc surface states. Probing its magnetic properties is crucial for understanding this correlated topological state. Here, using spin-polarized scanning tunneling microscopy/spectroscopy (STM/S) and non-contact atomic force microscopy (nc-AFM) combined with first-principle calculations, we report the discovery of localized spin-orbit polarons (SOPs) with three-fold rotation symmetry nucleated around single S-vacancies in Co3Sn2S2. The SOPs carry a magnetic moment and a large diamagnetic orbital magnetization of a possible topological origin associated relating to the diamagnetic circulating current around the S-vacancy. Appreciable magneto-elastic coupling of the SOP is detected by nc-AFM and STM. Our findings suggest that the SOPs can enhance magnetism and stability of the magnetic Weyl nodes for more robust time-reversal-symmetry-breaking topological phenomena. Controlled engineering of the SOPs may pave the way toward practical applications in functional quantum devices.

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Axion assisted Schwinger effect

Journal of High Energy Physics ◽

10.1007/jhep05(2021)001 ◽

2021 ◽

Vol 2021 (5) ◽

Author(s):

Valerie Domcke ◽

Yohei Ema ◽

Kyohei Mukaida

Keyword(s):

Electric Field ◽

Production Rate ◽

Strong Electric Field ◽

Background Field ◽

Chiral Anomaly ◽

Fermion Mass ◽

Anomaly Equation ◽

Electric And Magnetic Fields ◽

Schwinger Effect ◽

Momentum Transverse

Abstract We point out an enhancement of the pair production rate of charged fermions in a strong electric field in the presence of time dependent classical axion-like background field, which we call axion assisted Schwinger effect. While the standard Schwinger production rate is proportional to $$ \exp \left(-\pi \left({m}^2+{p}_T^2\right)/E\right) $$ exp − π m 2 + p T 2 / E , with m and pT denoting the fermion mass and its momentum transverse to the electric field E, the axion assisted Schwinger effect can be enhanced at large momenta to exp(−πm2/E). The origin of this enhancement is a coupling between the fermion spin and its momentum, induced by the axion velocity. As a non-trivial validation of our result, we show its invariance under field redefinitions associated with a chiral rotation and successfully reproduce the chiral anomaly equation in the presence of helical electric and magnetic fields. We comment on implications of this result for axion cosmology, focussing on axion inflation and axion dark matter detection.

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