scholarly journals A strongly robust type II Weyl fermion semimetal state in Ta3S2

2016 ◽  
Vol 2 (6) ◽  
pp. e1600295 ◽  
Author(s):  
Guoqing Chang ◽  
Su-Yang Xu ◽  
Daniel S. Sanchez ◽  
Shin-Ming Huang ◽  
Chi-Cheng Lee ◽  
...  
Keyword(s):  
Surface States ◽  
Insulator Transition ◽  
Type Ii ◽  
Weyl Semimetal ◽  
Tantalum Sulfide ◽  
Weyl Semimetals ◽  
Device Applications ◽  
Metal To Insulator Transition ◽  
Weyl Fermion ◽  
Topological Metal

Weyl semimetals are of great interest because they provide the first realization of the Weyl fermion, exhibit exotic quantum anomalies, and host Fermi arc surface states. The separation between Weyl nodes of opposite chirality gives a measure of the robustness of the Weyl semimetal state. To exploit the novel phenomena that arise from Weyl fermions in applications, it is crucially important to find robust separated Weyl nodes. We propose a methodology to design robust Weyl semimetals with well-separated Weyl nodes. Using this methodology as a guideline, we search among the material parameter space and identify by far the most robust and ideal Weyl semimetal candidate in the single-crystalline compound tantalum sulfide (Ta3S2) with new and novel properties beyond TaAs. Crucially, our results show that Ta3S2has the largestk-space separation between Weyl nodes among known Weyl semimetal candidates, which is about twice larger than the measured value in TaAs and 20 times larger than the predicted value in WTe2. Moreover, all Weyl nodes in Ta3S2are of type II. Therefore, Ta3S2is a type II Weyl semimetal. Furthermore, we predict that increasing the lattice by <4% can annihilate all Weyl nodes, driving a novel topological metal-to-insulator transition from a Weyl semimetal state to a topological insulator state. The robust type II Weyl semimetal state and the topological metal-to-insulator transition in Ta3S2are potentially useful in device applications. Our methodology can be generally applied to search for new Weyl semimetals.

scholarly journals Robust edge photocurrent response on layered type II Weyl semimetal WTe2

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Qinsheng Wang ◽  
Jingchuan Zheng ◽  
Yuan He ◽  
Jin Cao ◽  
Xin Liu ◽  
...  
Keyword(s):  
Energy Harvesting ◽  
Surface States ◽  
Separation Mechanism ◽  
Current Response ◽  
Type Ii ◽  
Nonlinear Optical Effect ◽  
Linear Dispersion ◽  
Weyl Semimetal ◽  
Quantum Materials ◽  
A Charge

AbstractPhotosensing and energy harvesting based on exotic properties of quantum materials and new operation principles have great potential to break the fundamental performance limit of conventional photodetectors and solar cells. Weyl semimetals have demonstrated novel optoelectronic properties that promise potential applications in photodetection and energy harvesting arising from their gapless linear dispersion and Berry field enhanced nonlinear optical effect at the vicinity of Weyl nodes. In this work, we demonstrate robust photocurrent generation at the edge of Td-WTe2, a type-II Weyl semimetal, due to crystalline-symmetry breaking along certain crystal fracture directions and possibly enhanced by robust fermi-arc type surface states. This edge response is highly generic and arises universally in a wide class of quantum materials with similar crystal symmetries. The robust and generic edge current response provides a charge separation mechanism for photosensing and energy harvesting over broad wavelength range.

scholarly journals Asymmetrical plasmonic absorber and reflector based on tilted Weyl semimetals

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Somayeh Oskoui Abdol ◽  
Babak Abdollahipour
Keyword(s):  
Thin Film ◽  
Surface Plasmon ◽  
Surface Plasmon Polariton ◽  
Optical Spectra ◽  
Optical Data ◽  
Type Ii ◽  
Fermi Surfaces ◽  
Weyl Semimetal ◽  
Weyl Semimetals ◽  
Plasmon Polariton

AbstractWe investigate the surface plasmon polariton dispersion and optical spectra of a thin film of tilted Weyl semimetal. Tilted Weyl semimetals possess tilted Weyl cones at the Weyl nodes and are categorized to type-I with closed Fermi surfaces and type-II with overtilted Weyl cones and open Fermi surfaces. We find that the surface plasmon polariton dispersion of this system is nonreciprocal even in the absence of the external magnetic field. Moreover, we demonstrate that the tilt parameter has a profound effect in controlling this nonreciprocity. We reveal that the thin film of type-II Weyl semimetal hosts the surface plasmon polariton modes with the negative group velocity. Furthermore, we show that the angular optical spectra of this structure are highly asymmetric and this angular asymmetry in the absorptivity and reflectivity depends profoundly on the tilt parameter of the tilted Weyl semimetal. These exciting features propose employing the tilted Weyl semimetals in optical sensing devices, optical data storage, and devices for quantum information processing.

scholarly journals Fermi-arc diversity on surface terminations of the magnetic Weyl semimetal Co3Sn2S2

Science ◽  
2019 ◽  
Vol 365 (6459) ◽  
pp. 1286-1291 ◽  
Author(s):  
Noam Morali ◽  
Rajib Batabyal ◽  
Pranab Kumar Nag ◽  
Enke Liu ◽  
Qiunan Xu ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Time Reversal ◽  
Surface States ◽  
Time Reversal Symmetry ◽  
Fermi Arc ◽  
Weyl Semimetal ◽  
Fermi Arcs ◽  
Bulk Surface ◽  
Weyl Semimetals ◽  
Node Connectivity

Bulk–surface correspondence in Weyl semimetals ensures the formation of topological “Fermi arc” surface bands whose existence is guaranteed by bulk Weyl nodes. By investigating three distinct surface terminations of the ferromagnetic semimetal Co3Sn2S2, we verify spectroscopically its classification as a time-reversal symmetry-broken Weyl semimetal. We show that the distinct surface potentials imposed by three different terminations modify the Fermi-arc contour and Weyl node connectivity. On the tin (Sn) surface, we identify intra–Brillouin zone Weyl node connectivity of Fermi arcs, whereas on cobalt (Co) termination, the connectivity is across adjacent Brillouin zones. On the sulfur (S) surface, Fermi arcs overlap with nontopological bulk and surface states. We thus resolve both topologically protected and nonprotected electronic properties of a Weyl semimetal.

DIELECTRIC FUNCTION, FRIEDEL OSCILLATION AND PLASMONS IN WEYL SEMIMETALS

2013 ◽  
Vol 27 (25) ◽  
pp. 1350177 ◽  
Author(s):  
MIN LV ◽  
SHOU-CHENG ZHANG
Keyword(s):  
Dielectric Function ◽  
Random Phase Approximation ◽  
Random Phase ◽  
R Factor ◽  
Fermion Systems ◽  
Weyl Semimetal ◽  
Weyl Semimetals ◽  
Friedel Oscillation ◽  
The One ◽  
Weyl Fermion

We calculate the dielectric function of a Weyl semimetal at arbitrary momentum q and frequency ω within the random-phase approximation. Taking the static limit, we calculated the Friedel oscillation and found that: (1) For a single Weyl point, the oscillation ~ sin (2kFr)/r4 falls off faster by an 1/r factor than the one in traditional 3D systems ~ cos (2kFr)/r3. This difference arises from the suppression of backward scattering in Weyl fermion systems; (2) For Weyl semimetal with two Weyl points, there are additional oscillations decaying as cos (Q ⋅ r)/r3 and cos (Q ± 2kF) ⋅ r/r3, where Q is the momentum difference between the two Weyl points. We also calculated the plasmon dispersion and found features distinct from those of conventional 3D metals.

scholarly journals Quasiparticle interference of surface states in the type-II Weyl semimetal WTe2

2017 ◽  
Vol 96 (16) ◽  
Author(s):  
Wenhan Zhang ◽  
Quansheng Wu ◽  
Lunyong Zhang ◽  
Sang-Wook Cheong ◽  
Alexey A. Soluyanov ◽  
...  
Keyword(s):  
Surface States ◽  
Type Ii ◽  
Quasiparticle Interference ◽  
Weyl Semimetal

scholarly journals Dynamical evolution of anisotropic response of type-II Weyl semimetal TaIrTe4 under ultrafast photoexcitation

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Xiao Zhuo ◽  
Jiawei Lai ◽  
Peng Yu ◽  
Ze Yu ◽  
Junchao Ma ◽  
...  
Keyword(s):  
High Performance ◽  
Wavelength Region ◽  
Dynamical Evolution ◽  
Quasi Equilibrium ◽  
Type Ii ◽  
Hot Carriers ◽  
Long Wavelength ◽  
Weyl Semimetal ◽  
Device Applications ◽  
Dynamical Conductivity

AbstractLayered type-II Weyl semimetals, such as WTe2, MoTe2, and TaIrTe4 have been demonstrated as a supreme photodetection material with topologically enhanced responsivity and specific sensitivity to the orbital angular momentum of light. Toward future device applications with high performance and ultrafast response, it is necessary to understand the dynamical processes of hot carriers and transient electronic properties of these materials under photoexcitation. In this work, mid-infrared ultrafast spectroscopy is performed to study the dynamical evolution of the anisotropic response of TaIrTe4. The dynamical relaxation of photoexcited carriers exhibits three exponential decay components relating to optical/acoustic phonon cooling and subsequent heat transfer to the substrate. The ultrafast transient dynamics imply that TaIrTe4 is an ideal material candidate for ultrafast optoelectronic applications, especially in the long-wavelength region. The angle-resolved measurement of transient reflection reveals that the reflectivity becomes less anisotropic in the quasi-equilibrium state, indicating a reduction in the anisotropy of dynamical conductivity in presence of photoexcited hot carriers. The results are indispensable in material engineering for polarization-sensitive optoelectronics and high field electronics.

scholarly journals Topological semimetal in honeycomb lattice LnSI

2017 ◽  
Vol 114 (40) ◽  
pp. 10596-10600 ◽  
Author(s):  
Simin Nie ◽  
Gang Xu ◽  
Fritz B. Prinz ◽  
Shou-cheng Zhang
Keyword(s):  
Condensed Matter ◽  
Surface States ◽  
Nodal Line ◽  
Honeycomb Lattice ◽  
Nodal Lines ◽  
Weyl Semimetal ◽  
The Standard Model ◽  
Weyl Semimetals ◽  
Topological Semimetals ◽  
The Right

Recognized as elementary particles in the standard model, Weyl fermions in condensed matter have received growing attention. However, most of the previously reported Weyl semimetals exhibit rather complicated electronic structures that, in turn, may have raised questions regarding the underlying physics. Here, we report promising topological phases that can be realized in specific honeycomb lattices, including ideal Weyl semimetal structures, 3D strong topological insulators, and nodal-line semimetal configurations. In particular, we highlight a semimetal featuring both Weyl nodes and nodal lines. Guided by this model, we showed that GdSI, the long-perceived ideal Weyl semimetal, has two pairs of Weyl nodes residing at the Fermi level and that LuSI (YSI) is a 3D strong topological insulator with the right-handed helical surface states. Our work provides a mechanism to study topological semimetals and proposes a platform for exploring the physics of Weyl semimetals as well as related device designs.

scholarly journals Surface superconductivity in the type II Weyl semimetal TaIrTe4

2019 ◽  
Vol 7 (3) ◽  
pp. 579-587 ◽  
Author(s):  
Ying Xing ◽  
Zhibin Shao ◽  
Jun Ge ◽  
Jiawei Luo ◽  
Jinhua Wang ◽  
...  
Keyword(s):  
Upper Critical Field ◽  
Surface States ◽  
P Wave ◽  
Scanning Tunneling ◽  
Type Ii ◽  
Surface Superconductivity ◽  
Weyl Semimetal ◽  
Ultralow Temperature ◽  
Transport Measurements ◽  
Majorana Modes

Abstract The search for unconventional superconductivity in Weyl semimetal materials is currently an exciting pursuit, since such superconducting phases could potentially be topologically non-trivial and host exotic Majorana modes. The layered material TaIrTe4 is a newly predicted time-reversal invariant type II Weyl semimetal with the minimum number of Weyl points. Here, we report the discovery of surface superconductivity in Weyl semimetal TaIrTe4. Our scanning tunneling microscopy/spectroscopy (STM/STS) visualizes Fermi arc surface states of TaIrTe4 that are consistent with the previous angle-resolved photoemission spectroscopy results. By a systematic study based on STS at ultralow temperature, we observe uniform superconducting gaps on the sample surface. The superconductivity is further confirmed by electrical transport measurements at ultralow temperature, with an onset transition temperature (Tc) up to 1.54 K being observed. The normalized upper critical field h*(T/Tc) behavior and the stability of the superconductivity against the ferromagnet indicate that the discovered superconductivity is unconventional with the p-wave pairing. The systematic STS, and thickness- and angular-dependent transport measurements reveal that the detected superconductivity is quasi-1D and occurs in the surface states. The discovery of the surface superconductivity in TaIrTe4 provides a new novel platform to explore topological superconductivity and Majorana modes.

scholarly journals Experimental discovery of a topological Weyl semimetal state in TaP

2015 ◽  
Vol 1 (10) ◽  
pp. e1501092 ◽  
Author(s):  
Su-Yang Xu ◽  
Ilya Belopolski ◽  
Daniel S. Sanchez ◽  
Chenglong Zhang ◽  
Guoqing Chang ◽  
...  
Keyword(s):  
Materials Science ◽  
Surface States ◽  
Photoemission Spectroscopy ◽  
New Horizons ◽  
Weyl Semimetal ◽  
Fermi Arcs ◽  
Experimental Discovery ◽  
Boundary Correspondence ◽  
First Time ◽  
Weyl Fermion

Weyl semimetals are expected to open up new horizons in physics and materials science because they provide the first realization of Weyl fermions and exhibit protected Fermi arc surface states. However, they had been found to be extremely rare in nature. Recently, a family of compounds, consisting of tantalum arsenide, tantalum phosphide (TaP), niobium arsenide, and niobium phosphide, was predicted as a Weyl semimetal candidates. We experimentally realize a Weyl semimetal state in TaP. Using photoemission spectroscopy, we directly observe the Weyl fermion cones and nodes in the bulk, and the Fermi arcs on the surface. Moreover, we find that the surface states show an unexpectedly rich structure, including both topological Fermi arcs and several topologically trivial closed contours in the vicinity of the Weyl points, which provides a promising platform to study the interplay between topological and trivial surface states on a Weyl semimetal’s surface. We directly demonstrate the bulk-boundary correspondence and establish the topologically nontrivial nature of the Weyl semimetal state in TaP, by resolving the net number of chiral edge modes on a closed path that encloses the Weyl node. This also provides, for the first time, an experimentally practical approach to demonstrating a bulk Weyl fermion from a surface state dispersion measured in photoemission.

scholarly journals Giant room temperature anomalous Hall effect and tunable topology in a ferromagnetic topological semimetal Co2MnAl

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Peigang Li ◽  
Jahyun Koo ◽  
Wei Ning ◽  
Jinguo Li ◽  
Leixin Miao ◽  
...  
Keyword(s):  
Hall Effect ◽  
Room Temperature ◽  
Transport Phenomena ◽  
Surface States ◽  
Anomalous Hall Effect ◽  
Spintronic Devices ◽  
Structure Topology ◽  
Weyl Semimetal ◽  
Weyl Semimetals ◽  
Record Value

Abstract Weyl semimetals exhibit unusual surface states and anomalous transport phenomena. It is hard to manipulate the band structure topology of specific Weyl materials. Topological transport phenomena usually appear at very low temperatures, which sets challenges for applications. In this work, we demonstrate the band topology modification via a weak magnetic field in a ferromagnetic Weyl semimetal candidate, Co2MnAl, at room temperature. We observe a tunable, giant anomalous Hall effect (AHE) induced by the transition involving Weyl points and nodal rings. The AHE conductivity is as large as that of a 3D quantum AHE, with the Hall angle (ΘH) reaching a record value ($$\tan {\Theta }^{H}=0.21$$ tan Θ H = 0.21 ) at the room temperature among magnetic conductors. Furthermore, we propose a material recipe to generate large AHE by gaping nodal rings without requiring Weyl points. Our work reveals an intrinsically magnetic platform to explore the interplay between magnetic dynamics and topological physics for developing spintronic devices.

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